stagefright: Do not drop encoded frames when writer is paused

Since the source drops input frames when paused, there is no
need to drop encoded frames in the writer as we run the risk
of dropping a key-frame.

Change-Id: I173f1ad2b610ad400ac43e0cd83ee1a7ed249b6b
CRs-Fixed: 682499
Merge "stagefright: Do not drop encoded frames when writer is paused" into du44