audioservice: fix hasMediaDynamicPolicy() for loopback and render policies

Exclude mixes with LOOPBACK + RENDER flags when looking for dynamic
policies matching media usage. As this is only used in the context
of sending becoming noisy intent we want to send the intent when playback
capture is active.

Bug: 137055231
Test: enable live caption and disconnect headset while music is playing
Change-Id: Ib3cd38f58c2ff78a2f2f13c5c22b637f9701e345