Fix tst_QFileSystemWatcher failure on Mac OS X

The watchFileAndItsDirectory() test would fail due to atime updates for
the first watched file coming up to 2 seconds after the file was closed.
Observation shows that the atime has a 2 second resolution on Mac OS X
using HFS+, so add an appropriate delay to make sure that the atime
update from the kqueue based file system watcher can dispatch all
updates.

Task-number: QTBUG-22744
Change-Id: Ie79af20d6b4c154021307c8a8f6d336369720337
Reviewed-by: Robin Burchell <robin+qt@viroteck.net>

tests/auto/corelib/io/qfilesystemwatcher/qfilesystemwatcher.pro

@@ -2,5 +2,3 @@ CONFIG += testcase parallel_test
 TARGET = tst_qfilesystemwatcher
 QT = core testlib
 SOURCES = tst_qfilesystemwatcher.cpp
-
-mac: CONFIG += insignificant_test # QTBUG-22744

tests/auto/corelib/io/qfilesystemwatcher/tst_qfilesystemwatcher.cpp

@@ -432,6 +432,11 @@ void tst_QFileSystemWatcher::watchFileAndItsDirectory()
     testFile.write(QByteArray("hello again"));
     testFile.close();
 
+#ifdef Q_OS_MAC
+    // wait again for the file's atime to be updated
+    QTest::qWait(2000);
+#endif
+
     QTRY_VERIFY(fileChangedSpy.count() > 0);
 
     //according to Qt 4 documentation: