GenericSource: Aggregate fewer audio i/p buffer for http streaming

Aggregating huge audio i/p buffer in streaming use case will cause
delay in fetching video i/p buffer and starving video decoder which
will eventually causing frame drops. In case of clips with abnormal
a/v interleaving, audio and video offsets can get too far apart
causing frequent underrun and staving both A/V decoder resulting
in choppy audio and video freeze.

To avoid this issue aggregate A/V buffer similar to  widevine
use-cases, reduce the audio buffer count to 8 and add an extra
video buffer.

Change-Id: I0afdbe11a1e427bd63a10f5cd874dbf6d102e6ab