Fix random selenium connection refused failure on web ui IT tests

11:36:18 web-ui-webdriver-tests.run-tests:
11:36:18 [INFO]      [exec] npm WARN optional Skipping failed optional dependency /chimp/chokidar/fsevents:
11:36:18 [INFO]      [exec] npm WARN notsup Not compatible with your operating system or architecture: fsevents@1.0.15
11:36:18 [INFO]      [exec] npm WARN nuxeo-web-ui-webdriver@1.0.0 No description
11:36:18 [INFO]      [exec] npm WARN nuxeo-web-ui-webdriver@1.0.0 No repository field.
11:36:19 [INFO]      [exec] > nuxeo-web-ui-webdriver@1.0.0 test /opt/jenkins/workspace/master/plugins_nuxeo-web-ui-master-master/nuxeo-web-ui-ftest/webdriver
11:36:19 [INFO]      [exec] > scripts/test.js
11:36:27 [INFO]      [exec] 
11:36:27 [INFO]      [exec] Master Chimp and become a testing Ninja! Check out our course: http://bit.ly/2btQaFu
11:36:27 [INFO]      [exec] 
11:36:27 [INFO]      [exec] 
11:36:27 [INFO]      [exec] [chimp] Running...
11:37:11 [INFO]      [exec] =======================================================================================
11:37:11 [INFO]      [exec] Selenium 2.0 / webdriver protocol bindings implementation with helper commands in nodejs.
11:37:11 [INFO]      [exec] For a complete list of commands, visit http://webdriver.io/api.html.
11:37:11 [INFO]      [exec] =======================================================================================
11:37:20 [INFO]      [exec] [chimp][helper] setupBrowserAndDDP had error
11:37:20 [INFO]      [exec] { Error: Connection refused
11:37:20 [INFO]      [exec]     at Object.Future.wait (/opt/jenkins/workspace/master/plugins_nuxeo-web-ui-master-master/nuxeo-web-ui-ftest/webdriver/node_modules/chimp/node_modules/xolvio-sync-webdriverio/node_modules/fibers/future.js:449:15)
11:37:20 [INFO]      [exec]     at Object.<anonymous> (/opt/jenkins/workspace/master/plugins_nuxeo-web-ui-master-master/nuxeo-web-ui-ftest/webdriver/node_modules/chimp/node_modules/xolvio-sync-webdriverio/node_modules/wdio-sync/build/index.js:345:27)
11:37:20 [INFO]      [exec]     at initBrowser (/opt/jenkins/workspace/master/plugins_nuxeo-web-ui-master-master/nuxeo-web-ui-ftest/webdriver/node_modules/chimp/dist/lib/chimp-helper.js:161:17)
11:37:20 [INFO]      [exec]     at Object.setupBrowserAndDDP (/opt/jenkins/workspace/master/plugins_nuxeo-web-ui-master-master/nuxeo-web-ui-ftest/webdriver/node_modules/chimp/dist/lib/chimp-helper.js:215:7)
11:37:20 [INFO]      [exec]     at /opt/jenkins/workspace/master/plugins_nuxeo-web-ui-master-master/nuxeo-web-ui-ftest/webdriver/node_modules/chimp/dist/lib/cucumberjs/hooks.js:21:24
11:37:20 [INFO]      [exec]     at /opt/jenkins/workspace/master/plugins_nuxeo-web-ui-master-master/nuxeo-web-ui-ftest/webdriver/node_modules/chimp/node_modules/meteor-promise/fiber_pool.js:32:39
11:37:20 [INFO]      [exec]     - - - - -
11:37:20 [INFO]      [exec]   message: 'Connection refused',
11:37:20 [INFO]      [exec]   type: 'RuntimeError',
11:37:20 [INFO]      [exec]   seleniumStack: 
11:37:20 [INFO]      [exec]    { status: 13,
11:37:20 [INFO]      [exec]      type: 'UnknownError',
11:37:20 [INFO]      [exec]      message: 'An unknown server-side error occurred while processing the command.',
11:37:20 [INFO]      [exec]      orgStatusMessage: 'Connection refused' } }
11:37:20 [INFO]      [exec] Error: Connection refused
11:37:20 [INFO]      [exec]     at Object.Future.wait (/opt/jenkins/workspace/master/plugins_nuxeo-web-ui-master-master/nuxeo-web-ui-ftest/webdriver/node_modules/chimp/node_modules/xolvio-sync-webdriverio/node_modules/fibers/future.js:449:15)
11:37:20 [INFO]      [exec]     at Object.<anonymous> (/opt/jenkins/workspace/master/plugins_nuxeo-web-ui-master-master/nuxeo-web-ui-ftest/webdriver/node_modules/chimp/node_modules/xolvio-sync-webdriverio/node_modules/wdio-sync/build/index.js:345:27)
11:37:20 [INFO]      [exec]     at initBrowser (/opt/jenkins/workspace/master/plugins_nuxeo-web-ui-master-master/nuxeo-web-ui-ftest/webdriver/node_modules/chimp/dist/lib/chimp-helper.js:161:17)
11:37:20 [INFO]      [exec]     at Object.setupBrowserAndDDP (/opt/jenkins/workspace/master/plugins_nuxeo-web-ui-master-master/nuxeo-web-ui-ftest/webdriver/node_modules/chimp/dist/lib/chimp-helper.js:215:7)
11:37:20 [INFO]      [exec]     at /opt/jenkins/workspace/master/plugins_nuxeo-web-ui-master-master/nuxeo-web-ui-ftest/webdriver/node_modules/chimp/dist/lib/cucumberjs/hooks.js:21:24
11:37:20 [INFO]      [exec]     at /opt/jenkins/workspace/master/plugins_nuxeo-web-ui-master-master/nuxeo-web-ui-ftest/webdriver/node_modules/chimp/node_modules/meteor-promise/fiber_pool.js:32:39
11:37:20 [INFO]      [exec]     - - - - -
11:37:20 [INFO]      [exec] Cucumber steps failed
11:37:20 [INFO]      [exec] /opt/jenkins/workspace/master/plugins_nuxeo-web-ui-master-master/nuxeo-web-ui-ftest/webdriver/node_modules/cucumber-junit/lib/cucumber_junit.js:196
11:37:20 [INFO]      [exec]         cucumberJson.forEach(function (featureJson) {
11:37:20 [INFO]      [exec]                     ^
11:37:20 [INFO]      [exec] TypeError: Cannot read property 'forEach' of null
11:37:20 [INFO]      [exec]     at cucumberJunit (/opt/jenkins/workspace/master/plugins_nuxeo-web-ui-master-master/nuxeo-web-ui-ftest/webdriver/node_modules/cucumber-junit/lib/cucumber_junit.js:196:21)
11:37:20 [INFO]      [exec]     at writeJUnitReport (/opt/jenkins/workspace/master/plugins_nuxeo-web-ui-master-master/nuxeo-web-ui-ftest/webdriver/scripts/test.js:28:26)
11:37:20 [INFO]      [exec]     at ChildProcess.chimp.on (/opt/jenkins/workspace/master/plugins_nuxeo-web-ui-master-master/nuxeo-web-ui-ftest/webdriver/scripts/test.js:37:3)
11:37:20 [INFO]      [exec]     at emitTwo (events.js:106:13)
11:37:20 [INFO]      [exec]     at ChildProcess.emit (events.js:191:7)
11:37:20 [INFO]      [exec]     at maybeClose (internal/child_process.js:852:16)
11:37:20 [INFO]      [exec]     at Process.ChildProcess._handle.onexit (internal/child_process.js:215:5)
11:37:20 [INFO]      [exec] npm ERR! Test failed.  See above for more details.
11:37:20 [ERROR]