Change the default time scale for audio/video track during recording

and reduce rounding errors in calculating the sample duration

- Default time scale for tracks other than audio is set to 90000.
- Audio track by default uses the audio sampling rate as the time scale.
- Default movie time scale remains to be 1000.
- The default time scale values will be overwritten by a user-supplied value if exits.

Change-Id: I81b40ed0626ea45e9fd24a89e21a2c5a4a2c3415