policy_hal: Fix check for direct pcm

-mediaplayer now opens a sink with DIRECT_PCM flag for eligible
playbacks, now if setPlayback rate api is triggered for
mediaplayer object,fall back to deep buffer output should happen.
But as the DIRECT_PCM flag is not removed from the requested flags,
the same direct output gets selected.
-Ensure that DIRECT_PCM flag is removed always if present,
before query for output, otherwise even when no direct output
is required, might end up with one.

Change-Id: Ie27e90851a0de4a6a6c2dc205a8ed9e281663626