SoundRecorder: add a focus listener to change record state

Recording won't stop when pressing hook key to play music. If music
start to play, SoundRecorder will lose audio focus, add the listener
to change record state.

Change-Id: Icc3422dd1c35bcf7914f1d4ad4250aad5b10c703
CRs-Fixed: 668528
SoundRecorder: reset VU Meter upon pause

Change-Id: I13492a2685119b0622253b7c4837219d7ee549a2
CRs-Fixed: 671783