highfidelity/hifi — pull request #1664 by ZappoMan (2014-01-23 22:58:46+00:00)
Title: fix random crash on interface shutdown

I believe this will fix some of the random occurrences of this crash...

```
Thread 4 Crashed:: QThread
0 QtCore	0x000000010ad1c850 QMutexPrivate::allocate() + 208
1 QtCore	0x000000010ad1c48b QBasicMutex::lockInternal(int) + 155
2 QtCore	0x000000010ad1c3d7 QMutex::lock() + 119
3 QtCore	0x000000010ad1f403 QThread::exit(int) + 35
4 interface	0x000000010a63b91b GenericThread::threadRoutine() + 139 (GenericThread.cpp:72)
5 interface	0x000000010a651c8b GenericThread::qt_static_metacall(QObject*, QMetaObject::Call, int, void**) + 107 (moc_GenericThread.cpp:75)
6 QtCore	0x000000010af0e591 QMetaObject::activate(QObject*, int, int, void**) + 2593
7 QtCore	0x000000010ad22e47 QThreadPrivate::start(void*) + 423
8 libsystem_c.dylib	0x00007fff89ded7a2 _pthread_start + 327
9 libsystem_c.dylib	0x00007fff89dda1e1 thread_start + 13
```