Preventing camera button to get into wrong state when pressed in succession (camera-haleakala)

- Adding methods to ButtonManager to enable/disable camera button explicitly
- Camera button cannot be enabled during initialization if it was explicitly disabled
- PhotoModule, VideoModule and CaptureModule enable/disable camera button on camera switch
- Capture button is disabled before requesting the camera switch
- Capture button is re-enabled once the camera open confirmation is received

Bug: 20693214
Change-Id: I6383c705eee0a82397b975332cf37bbcd5913128
4 files changed