Eliminate recording sound by starting the video track before audio track.

Due to the variable delays in the system, the recording sound can still be heard
if the audio track is started early. This happens even after we suppress a relative
long period of initial audio for a recording session. By starting the video track
before the audio track, we effectively play the recording sound earlier.

bug - 3371141

Change-Id: I2cccf77eae953d96827fc080c618b1d962445c26