Fix random failure on BatchManagerFixture.testBatchConcurrency

java.lang.AssertionError
	at org.junit.Assert.fail(Assert.java:86)
	at org.junit.Assert.assertTrue(Assert.java:41)
	at org.junit.Assert.assertNotNull(Assert.java:621)
	at org.junit.Assert.assertNotNull(Assert.java:631)
	at org.nuxeo.ecm.automation.server.jaxrs.batch.BatchManagerFixture.testBatchConcurrency(BatchManagerFixture.java:353)
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.lang.reflect.Method.invoke(Method.java:498)
	at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:47)
	at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
	at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:44)
	at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17)
	at org.nuxeo.runtime.test.runner.FeaturesRunner$15.evaluate(FeaturesRunner.java:467)
	at org.nuxeo.runtime.test.runner.FeaturesRunner$BeforeMethodRunStatement.evaluate(FeaturesRunner.java:346)
	at org.nuxeo.runtime.test.runner.FeaturesRunner$BeforeSetupStatement.evaluate(FeaturesRunner.java:362)
	at org.nuxeo.runtime.test.runner.FeaturesRunner$AfterMethodRunStatement.evaluate(FeaturesRunner.java:393)
	at org.nuxeo.runtime.test.runner.FeaturesRunner$AfterTeardownStatement.evaluate(FeaturesRunner.java:412)
	at org.nuxeo.runtime.test.runner.FeaturesRunner$RulesFactory$1.evaluate(FeaturesRunner.java:525)
	at org.nuxeo.runtime.test.runner.RuntimeDeployment$DeploymentStatement.evaluate(RuntimeDeployment.java:270)
	at org.nuxeo.runtime.test.runner.RuntimeFeature$2$1.evaluate(RuntimeFeature.java:124)
	at org.junit.rules.RunRules.evaluate(RunRules.java:20)
	at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:271)
	at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:70)
	at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:50)
	at org.junit.runners.ParentRunner$3.run(ParentRunner.java:238)
	at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:63)
	at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:236)
	at org.junit.runners.ParentRunner.access$000(ParentRunner.java:53)
	at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:229)
	at org.nuxeo.runtime.test.runner.FeaturesRunner$AfterClassStatement.evaluate(FeaturesRunner.java:285)
	at org.nuxeo.runtime.test.runner.FeaturesRunner$RulesFactory$1.evaluate(FeaturesRunner.java:525)
	at org.nuxeo.runtime.test.runner.FeaturesRunner$BeforeClassStatement.evaluate(FeaturesRunner.java:268)
	at org.junit.rules.RunRules.evaluate(RunRules.java:20)
	at org.junit.runners.ParentRunner.run(ParentRunner.java:309)
	at org.junit.runners.Suite.runChild(Suite.java:127)
	at org.junit.runners.Suite.runChild(Suite.java:26)
	at org.junit.runners.ParentRunner$3.run(ParentRunner.java:238)
	at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:63)
	at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:236)
	at org.junit.runners.ParentRunner.access$000(ParentRunner.java:53)
	at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:229)
	at org.junit.runners.ParentRunner.run(ParentRunner.java:309)
	at org.junit.runners.Suite.runChild(Suite.java:127)
	at org.junit.runners.Suite.runChild(Suite.java:26)
	at org.junit.runners.ParentRunner$3.run(ParentRunner.java:238)
	at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:63)
	at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:236)
	at org.junit.runners.ParentRunner.access$000(ParentRunner.java:53)
	at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:229)
	at org.junit.runners.ParentRunner.run(ParentRunner.java:309)
	at org.junit.runner.JUnitCore.run(JUnitCore.java:160)
	at org.junit.runner.JUnitCore.run(JUnitCore.java:138)
	at org.apache.maven.surefire.junitcore.JUnitCoreWrapper.createRequestAndRun(JUnitCoreWrapper.java:113)
	at org.apache.maven.surefire.junitcore.JUnitCoreWrapper.executeEager(JUnitCoreWrapper.java:85)
	at org.apache.maven.surefire.junitcore.JUnitCoreWrapper.execute(JUnitCoreWrapper.java:54)
	at org.apache.maven.surefire.junitcore.JUnitCoreProvider.invoke(JUnitCoreProvider.java:134)
	at org.apache.maven.surefire.booter.ForkedBooter.invokeProviderInSameClassLoader(ForkedBooter.java:200)
	at org.apache.maven.surefire.booter.ForkedBooter.runSuitesInProcess(ForkedBooter.java:153)
	at org.apache.maven.surefire.booter.ForkedBooter.main(ForkedBooter.java:103)