libstagefright: Add error handling in mediacodecsource

During camcorder recording, if encoder throws an error,
it intimates error to media codec source.
In such error cases, added functionality to stop puller
and clean up the graph to avoid memory leaks.

Bug: 34870133
Test: Video Recording.

Author: Uma Mehta <umamehta@codeaurora.org>

Change-Id: I487d96f855f541033e8ec7872e86d00bafb96daf