Check the credentials server before each funkload test fails to contact it

10:59:40 funkload-tests.funkload-ctl-daemons:
10:59:40 [INFO]      [exec] Starting monitor server at http://0.0.0.0:55502/ as daemon.
10:59:41 [INFO]      [exec] Starting file_credential server at http://localhost:55501/ as daemon.
10:59:41 [INFO]      [echo] Handling list element: test_rest.py[testWriter:testReader]
10:59:41 [INFO] Managed version set on org.nuxeo:nuxeo-ftest:zip:1.7.14
10:59:41 [INFO]     [unzip] Expanding: /opt/jenkins/.m2/repository/org/nuxeo/nuxeo-ftest/1.7.14/nuxeo-ftest-1.7.14.zip into /opt/jenkins/workspace/docker-test-funkload/nuxeo/nuxeo-distribution/nuxeo-distribution-dm/ftest/funkload/target
10:59:41 
10:59:41 funkload-tests.fl-run-tests:
10:59:41 [INFO]      [echo] Suite: test_rest.py - Test: testWriter
10:59:41 [INFO]      [echo] Running: fl-run-test -v --simple-fetch test_rest.py -e testWriter -u http://localhost:8080/nuxeo --no-color
10:59:43 [INFO]      [exec] testWriter (test_rest.Rest) ... ERROR
10:59:43 [INFO]      [exec] ======================================================================
10:59:43 [INFO]      [exec] ERROR: testWriter (test_rest.Rest)
10:59:43 [INFO]      [exec] ----------------------------------------------------------------------
10:59:43 [INFO]      [exec] Traceback (most recent call last):
10:59:43 [INFO]      [exec]   File "/usr/local/lib/python2.7/dist-packages/funkload-1.17.0-py2.7.egg/funkload/FunkLoadTestCase.py", line 965, in __call__
10:59:43 [INFO]      [exec]     self.setUp()
10:59:43 [INFO]      [exec]   File "/opt/jenkins/workspace/docker-test-funkload/nuxeo/nuxeo-distribution/nuxeo-distribution-dm/ftest/funkload/test_rest.py", line 45, in setUp
10:59:43 [INFO]      [exec]     'admin')
10:59:43 [INFO]      [exec]   File "/usr/local/lib/python2.7/dist-packages/funkload-1.17.0-py2.7.egg/funkload/utils.py", line 185, in xmlrpc_get_credential
10:59:43 [INFO]      [exec]     'to start the credential server.' % url)
10:59:43 [INFO]      [exec] error: No Credential server reachable at http://localhost:55501, use fl-credential-ctl to start the credential server.
10:59:43 [INFO]      [exec] ----------------------------------------------------------------------
10:59:43 [INFO]      [exec] Ran 1 test in 0.002s
10:59:43 [INFO]      [exec] FAILED (errors=1)