Audio stops after seeking AVI clip with MP3 audio (special contents without proper key samples)

During seek in AVI, nearest Sync sample was searched both for
audio and video. Sync samples are useful only in case of
video. We can ignore Sync field for non-video tracks.

Change-Id: Ibaeda8f14afb83905e19087625a7d72fb1b3c8d6
Signed-off-by: Arulselvan M <arulselvan.m@intel.com>
Signed-off-by: Jin Wei <wei.a.jin@intel.com>