org.eclipse.jface.text.tests.reconciler.AbstractReconcilerTest.testDirtyingWhenClean fails randomly

[fedejeanne]

e.g. in #2407

java.lang.AssertionError
	at org.junit.Assert.fail(Assert.java:87)
	at org.junit.Assert.assertTrue(Assert.java:42)
	at org.junit.Assert.assertFalse(Assert.java:65)
	at org.junit.Assert.assertFalse(Assert.java:75)
	at org.eclipse.jface.text.tests.reconciler.AbstractReconcilerTest.testDirtyingWhenClean(AbstractReconcilerTest.java:253)
...