audioflinger: Fix to set correct volume in Tunnel playback

- After a pause and resume, tunnel playback volume is always
  set to maximum irrespective of the volume value before pause.
- The cause for this is, the stream volume is not used to set
  the volume in directaudiotrack.
- Fix is to use the stream volume to set volume during tunnel
  playback.

Change-Id: I59cda146ed88bd5c4186aeb9ae5d165f4a27493f
CRs-fixed: 452285
libstagefright: Check for duration > 0 to avoid DivideByZero crash

- duration = 0 can cause divide by zero and for this clip duration
  is indiacted as 0.
- check for duration > 0 rather than duration >= 0

Change-Id: I58ccacbf7ede892dff9626715162ea7b1f2ddbc6
CRs-Fixed: 451855