tst_QSoundEffect::testSetSourceWhilePlaying() fails often in the CI

********* Start testing of tst_QSoundEffect *********
Config: Using QtTest library 5.8.0, Qt 5.8.0 (x86_64-little_endian-lp64 shared (dynamic) release build; by GCC 4.8.2)
PASS   : tst_QSoundEffect::initTestCase()
PASS   : tst_QSoundEffect::testSource()
PASS   : tst_QSoundEffect::testLooping()
PASS   : tst_QSoundEffect::testVolume()
PASS   : tst_QSoundEffect::testMuting()
QWARN  : tst_QSoundEffect::testPlaying() QSoundEffect(pulseaudio): Error decoding source
PASS   : tst_QSoundEffect::testPlaying()
QWARN  : tst_QSoundEffect::testStatus() QSoundEffect(pulseaudio): Error decoding source
PASS   : tst_QSoundEffect::testStatus()
PASS   : tst_QSoundEffect::testDestroyWhilePlaying()
PASS   : tst_QSoundEffect::testDestroyWhileRestartPlaying()
PASS   : tst_QSoundEffect::testSetSourceWhileLoading()

========= Received signal, dumping stack ==============
GNU gdb (Ubuntu 7.7.1-0ubuntu5~14.04.2) 7.7.1
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Attaching to process 5377
(gdb) ========= End of stack trace ==============
QFATAL : tst_QSoundEffect::testSetSourceWhilePlaying() Received signal 11
         Function time: 1525ms Total time: 28804ms
FAIL!  : tst_QSoundEffect::testSetSourceWhilePlaying() Received a fatal error.
   Loc: [Unknown file(0)]
Totals: 10 passed, 1 failed, 0 skipped, 0 blacklisted, 29645ms
********* Finished testing of tst_QSoundEffect *********
make: *** [check] Aborted (core dumped)

agent:2016/08/31 13:26:28 build.go:200: Process finished with error: exit status 2
agent:2016/08/31 13:26:28 build.go:152: Error reading from stdout/err: exit status 2
agent:2016/08/31 13:26:48 build.go:270: [make check -j1] 900 1200
/home/qt/work/qt/qtmultimedia/tests/auto/integration/qsoundeffect/target_wrapper.sh  ./tst_qsoundeffect testSetSourceWhilePlaying