Cleanup AudioTrack::getMinFrameCount error handling

Guarantee to return a non-zero frameCount for return status NO_ERROR;

Return the correct specific status_t if any of the AudioSystem APIs fail,
instead of the generic NO_INIT.

API change: getMinFramCount no longer defaults to zero on error, so
callers _must_ check the return status.  This change makes
getMinFrameCount more like other APIs.  All known callers were reviewed,
and they do check the return status.

Change-Id: I4a8342a75ee89a068c23c84b8380ed9d1b968507