Fix random TestExportedZipImporterPlugin.testImportViaFileManager

org.junit.ComparisonFailure: expected:<[TestExportedZipImporterPlugin_530610961134920123,zip]> but was:<[Source Workspace]>
	at org.junit.Assert.assertEquals(Assert.java:115)
	at org.junit.Assert.assertEquals(Assert.java:144)
	at org.nuxeo.ecm.platform.filemanager.TestExportedZipImporterPlugin.testImportViaFileManager(TestExportedZipImporterPlugin.java:153)
	at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
	at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.base/java.lang.reflect.Method.invoke(Method.java:566)
	at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:50)
	at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
	at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:47)
	at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17)
	at org.nuxeo.runtime.test.runner.FeaturesRunner$BeforeMethodRunStatement.evaluate(FeaturesRunner.java:292)
	at org.nuxeo.runtime.test.runner.FeaturesRunner$BeforeSetupStatement.evaluate(FeaturesRunner.java:306)
	at org.nuxeo.runtime.test.runner.FeaturesRunner$AfterMethodRunStatement.evaluate(FeaturesRunner.java:329)
	at org.junit.internal.runners.statements.RunAfters.evaluate(RunAfters.java:27)
	at org.nuxeo.runtime.test.runner.FeaturesRunner$AfterTeardownStatement.evaluate(FeaturesRunner.java:346)
	at org.nuxeo.runtime.test.runner.FeaturesRunner$RulesFactory$1.evaluate(FeaturesRunner.java:419)
	at org.nuxeo.runtime.test.runner.RuntimeDeployment$DeploymentStatement.evaluate(RuntimeDeployment.java:326)
	at org.junit.rules.RunRules.evaluate(RunRules.java:20)