Disconnect external cameras if sensor privacy enabled

 If the camera device does not support mute test patterns, then it
 will be disconnected when the camera sensor privacy is enabled.

Bug: 182204067
Test: Connect an USB camera.
 Enable camera privacy toggle.
 Apps using the camera should get a blank preview (camera disconnected)
Change-Id: I7298e16190d6416abbe981adcbb1f87637fcaf77