Revisit logging in MediaRouter and MediaSessionRecord

This limits excessive logs from MediaRouter and MediaSessionRecord
- MediaRouter: Leave log only if there's change in the audio route.
- MediaSessionRecord: Leave log for the controller callback instead of
    dumping verbose stack traces.

Bug: 36497125
Test: Manual test
Change-Id: Ie0fe9f33388d1aa9f25c26b3b3f7c71fec409ba8