LibAAH_RTP: Fix an issue which crept in during code review.

Fix a mistake which came in as part of a merge conflict resolution
during code review of the recent unicast mode refactor of LibAAH_RTP.
Nop packet which were supposed to carry TS transformations for the
pause state accidentally got flagged as Flush operations.  The flush
packet successfully carried the TS transformation, but also had the
undesired side effect of constantly flushing the stream.

Change-Id: I4c6aa0043fc274a1d7e880ed1d19cf277f22194b
Signed-off-by: John Grossman <johngro@google.com>