audio flinger: return port ID as track ID to client

Return the port ID allocated by audio policy manager instead of the
internal track ID allocated by audio flinger when an AudioTrack or
AudioRecord is created.
This information is more useful for logs and allows to associate information coming
from audiopolicy manager with a specific client instance.

Bug: 111438757
Test: Manual playback and capture tests
Change-Id: Ib467d8fcc34d9a8aa7bcaac0770a741982b847c5