mediaplayer: Fix AudioFlinger create track failure

- AudioFlinger track creation fails after mediaserver crash
- Mediaplayer doesn't register for new sessionId value if
mediaserver crashes during a song switch of music player
and it uses the old sessionId though sessionId values are
reset by AudioFlinger.
  AudioFlinger assigns the same sessionId to Tone Generator
and since strategies of these two session differ it would
result in track creation failure.
- Fix this issue by registering for new sessionId for
mediaplayer if mediaserver crashes in idle state

Change-Id: I25c01842d7df4f4eb0f9d084a648d6d1a88fa926
CRs-fixed: 271002