audio policy: reduce mute time when invalidating tracks

Replace fixed 2 seconds mute time in checkOutputForStrategy() by
a variable time based on actual maximum output latency.

Also fix problem where src outputs where queried from mOutputs list
instead of from mPreviousOutputs.

Bug: 70632415
Test: manual connections/disconnection of BT A2DP and USB headset
Change-Id: I3a9ea915a134d95a2dc5abea2fbfe6152f147e80