Fixes for missing audio device.
Merge pull request #3970 from ey6es/master

Fixes for missing audio device.
Fix for crash on exit due to cache references' not being cleared.
Merge pull request #3971 from ey6es/master

Fix for crash on exit due to cache references' not being cleared.
Merge branch 'master' of https://github.com/highfidelity/hifi into InterfaceConfigEctomy