Fix Nuxeo Retention tests

The job is failing since october 27th: https://qa.nuxeo.org/jenkins/job/Sandbox/job/sandbox_nuxeo-retention-master/lastCompletedBuild/#showFailuresLink

• org.nuxeo.ecm.retention.test.RetentionServiceTest.testStartRetentionWithDelay

  org.junit.ComparisonFailure: expected:<[active]> but was:<[unmanaged]>

• org.nuxeo.ecm.retention.test.RetentionServiceTest.org.nuxeo.ecm.retention.test.RetentionServiceTest

  java.lang.AssertionError: invoke on features error [Holder [type=class org.nuxeo.ecm.automation.test.AutomationFeature], Holder [type=class org.nuxeo.ecm.platform.test.PlatformFeature], Holder [type=class org.nuxeo.directory.test.DirectoryFeature], Holder [type=class org.nuxeo.ecm.platform.login.test.ClientLoginFeature], Holder [type=class org.nuxeo.ecm.core.test.CoreFeature], Holder [type=class org.nuxeo.ecm.core.test.TransactionalFeature], Holder [type=class org.nuxeo.runtime.test.runner.ContainerFeature], Holder [type=class org.nuxeo.runtime.test.runner.RuntimeFeature], Holder [type=class org.nuxeo.runtime.test.runner.RandomBug$Feature], Holder [type=class org.nuxeo.runtime.test.runner.ConditionalIgnoreRule$Feature], Holder [type=class org.nuxeo.runtime.test.runner.MDCFeature]]
  

• org.nuxeo.ecm.retention.test.RetentionServiceTest.testStartRetentionOnModifiedEvent

  java.lang.AssertionError: expected:<2019> but was:<2018>

Fixing the tests is required to release the addon.