Fixed a native crash due to unexpected state at destroy time when encoder...

Fixed a native crash due to unexpected state at destroy time when encoder component's source fails to start

o Encoder component initializes to be in the state of EXECUTING before its source gets started, because we wanted to be able
  to configure the source to use the advertised number of input buffers. However, if the source fails to start, then the encoder
  ends up in the state of EXECUTING when OMXCodec object gets destroyed. As a result, the assertion on the expected state in
  OMXCodec's constructor fails. The fix is to stop the video encoder component right way when its source fails to start so to
  bring the state of the encoder component back to the expected state.

o related-to-bug: 7045494

Change-Id: I6d4a221eb809d7137f53e58098a04816998f7a25