audio: ensure effect chain with specific session id is unique

It's possible that tracks with the same session id running on various
playback outputs, which causes effect chain being created on the same
session twice. As a result, the same effect engine will be released
twice as the same context is reused.

Output that has effect chain with same session id is more preferable.

Test: No regression with Play Music and Effects
Bug: 123082420
Bug: 123237974
Merged-In: I690ea3cb942d1fdc96b46048e271557d48000f43
Change-Id: I690ea3cb942d1fdc96b46048e271557d48000f43
(cherry picked from commit 9aeb1770)