Attempt to stabilize FileTreeIterator test on Windows

My guess is that the higher resolution of timestamps provided by Java on
Windows causes this test to occasionally fail.

Bug: 396662
Change-Id: Ia10d76e95fe6156c7ad05972619160e461606805

org.eclipse.jgit.test/tst/org/eclipse/jgit/treewalk/FileTreeIteratorTest.java

@@ -253,14 +253,16 @@ public class FileTreeIteratorTest extends RepositoryTestCase {
 		// Hopefully fsTick will make sure our entry gets smudged
 		fsTick(f);
 		writeTrashFile("file", "content");
+		long lastModified = f.lastModified();
 		git.add().addFilepattern("file").call();
 		writeTrashFile("file", "conten2");
+		f.setLastModified(lastModified);
 		DirCacheEntry dce = db.readDirCache().getEntry("file");
 		FileTreeIterator fti = new FileTreeIterator(trash, db.getFS(), db
 				.getConfig().get(WorkingTreeOptions.KEY));
 		while (!fti.getEntryPathString().equals("file"))
 			fti.next(1);
-		// If the fsTick trick does not work we could skip the compareMetaData
+		// If the rounding trick does not work we could skip the compareMetaData
 		// test and hope that we are usually testing the intended code path.
 		assertEquals(MetadataDiff.SMUDGED, fti.compareMetadata(dce));
 		assertTrue(fti.isModified(dce, false));