audio: update flags for selection of VoIP direct output

Ringtone mute is observed in LINE app MT call over BT headset.
VoIP direct output isn't returned due to incorrect flags update.
Primary output is returned even though the FLAG_DIRECT is set,
this in turn causing issues when renderer queries for getPosition(),
which is resulting in mute. Fix this by updating flags, so that
track gets VoIP direct output in this scenario.

Change-Id: I6d570ae6ed9e0a7506cb29be5b41687417b7d221
CRs-Fixed: 893558