media: Fix mpeg2ts muxer.

1) Fix the CSD handling due to missing timestamp in CSD buffer.
2) Remove the concatenation of audio frames and write out every audio frame
immediately to unblock the video frame write out.
3) Unblock audio track thread after geting CSD.

Bug:21620607
Change-Id: I4926ef7202e1692a2c50a5e8158a9cfb19d9ed3f