audio: apply volume on DirectOutput streams

- Call stream->set_volume to apply volume on
  particular stream of DirectOutputs

Change-Id: I98e3b856ee508d407f893afad66caade5eda3e4a
CRs-Fixed: 445953
libstagefright: Adjustment for TunnelPlayer buffer size

- Make necessary adjustments to align the buffer size
  for TunnelPlayer to satisfy the following conditions
- Buffer size is a multiple of LCM(1,2,4,6,8)
- Buffer size is aligned to 4k.
CRs-Fixed: 447274, 442365

Change-Id: I1b7f9ac3cf8ff86f972a8b6798bfcff3a4ba7c64
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