tst_QMediaObject ::notifySignals() is flaky on Windows

 	C:\Utils\Jom\jom.exe -f Makefile.Release check
 	call C:\Users\qt\work\qt\qtmultimedia\tests\auto\unit\qmediaobject\target_wrapper.bat  release\tst_qmediaobject.exe -o C:\Users\qt\work\testresults\tests\auto\unit\qmediaobject650446180,xml -o -,txt
 ********* Start testing of tst_QMediaObject *********
 Config: Using QtTest library 5.11.0, Qt 5.11.0 (x86_64-little_endian-llp64 shared (dynamic) release build; by MSVC 2015)
 PASS   : tst_QMediaObject::initTestCase()
 PASS   : tst_QMediaObject::propertyWatch()
 FAIL!  : tst_QMediaObject::notifySignals(single 750ms) 'elapsed < expectedElapsed' returned FALSE. (elapsed: 1234, expected: 1125)
 tst_qmediaobject.cpp(303) : failure location
 FAIL!  : tst_QMediaObject::notifySignals(single 600ms) 'elapsed < expectedElapsed' returned FALSE. (elapsed: 1161, expected: 900)
 tst_qmediaobject.cpp(303) : failure location
 FAIL!  : tst_QMediaObject::notifySignals(x3 300ms) 'elapsed < expectedElapsed' returned FALSE. (elapsed: 3006, expected: 1350)
 tst_qmediaobject.cpp(303) : failure location
 FAIL!  : tst_QMediaObject::notifySignals(x5 180ms) 'elapsed < expectedElapsed' returned FALSE. (elapsed: 2589, expected: 1350)
 tst_qmediaobject.cpp(303) : failure location
 PASS   : tst_QMediaObject::notifyInterval(single 750ms)
 PASS   : tst_QMediaObject::notifyInterval(single 600ms)
 PASS   : tst_QMediaObject::notifyInterval(x3 300ms)
 PASS   : tst_QMediaObject::notifyInterval(x5 180ms)
 PASS   : tst_QMediaObject::nullMetaDataControl()
 PASS   : tst_QMediaObject::isMetaDataAvailable()
 PASS   : tst_QMediaObject::metaDataChanged()
 PASS   : tst_QMediaObject::metaData()
 PASS   : tst_QMediaObject::availability()
 PASS   : tst_QMediaObject::service()
 PASS   : tst_QMediaObject::cleanupTestCase()
 Totals: 13 passed, 4 failed, 0 skipped, 0 blacklisted, 10098ms
 ********* Finished testing of tst_QMediaObject *********
 jom: C:\Users\qt\work\qt\qtmultimedia\tests\auto\unit\qmediaobject\Makefile.Release [check] Error 4
 jom: C:\Users\qt\work\qt\qtmultimedia\tests\auto\unit\qmediaobject\Makefile [release-check] Error 2
 
 agent:2018/04/16 07:56:49 build.go:187: Process finished with error: exit status 2
 agent:2018/04/16 07:56:49 build.go:139: Error reading from stdout/err: exit status 2
 agent:2018/04/16 07:57:09 build.go:262: [c:\users\qt\MSVC2015.bat jom check] 900 900
 
 C:\Users\qt\work\qt\qtmultimedia\tests\auto\unit\qmediaobject>call "C:\Program Files (x86)\Microsoft Visual Studio 14.0\VC\vcvarsall.bat" amd64  
 
 jom 1.1.2 - empower your cores
 
 	C:\Utils\Jom\jom.exe -f Makefile.Release check
 	call C:\Users\qt\work\qt\qtmultimedia\tests\auto\unit\qmediaobject\target_wrapper.bat  release\tst_qmediaobject.exe notifySignals
 ********* Start testing of tst_QMediaObject *********
 Config: Using QtTest library 5.11.0, Qt 5.11.0 (x86_64-little_endian-llp64 shared (dynamic) release build; by MSVC 2015)
 PASS   : tst_QMediaObject::initTestCase()
 FAIL!  : tst_QMediaObject::notifySignals(single 750ms) 'elapsed < expectedElapsed' returned FALSE. (elapsed: 2104, expected: 1125)
 tst_qmediaobject.cpp(303) : failure location
 FAIL!  : tst_QMediaObject::notifySignals(single 600ms) 'elapsed < expectedElapsed' returned FALSE. (elapsed: 5488, expected: 900)
 tst_qmediaobject.cpp(303) : failure location
 FAIL!  : tst_QMediaObject::notifySignals(x3 300ms) 'elapsed < expectedElapsed' returned FALSE. (elapsed: 6111, expected: 1350)
 tst_qmediaobject.cpp(303) : failure location
 FAIL!  : tst_QMediaObject::notifySignals(x5 180ms) 'elapsed < expectedElapsed' returned FALSE. (elapsed: 3843, expected: 1350)
 tst_qmediaobject.cpp(303) : failure location
 PASS   : tst_QMediaObject::cleanupTestCase()
 Totals: 2 passed, 4 failed, 0 skipped, 0 blacklisted, 17555ms