SchedulingPolicyService: add extra check for the target UID

When audio HAL is asking to boost priority of its I/O thread
it passes TID to the audio service. To reduce the chance of
boosting priority of a wrong thread due to PID wrapping,
ensure that the target thread belongs to the right UID.

Bug: 181148259
Test: manual validation of thread priorities
Change-Id: I73dc30492b292bede95e6fc38f318ef966f417ca