WebRTCDemo: couldn't run a second time. The reason is voe could register/unregister for each run, but vie would expect initialization only once per process.
This cl is to teach videocapture android how to deinitialize and allow it to be re-initializable.

BUG=3284
TEST=ManualTest
R=fischman@webrtc.org

Review URL: https://webrtc-codereview.appspot.com/15429004

git-svn-id: http://webrtc.googlecode.com/svn/trunk@6167 4adac7df-926f-26a2-2b94-8c16560cd09d