Use actual device instead of requested device to enter a bluetooth

route.

Currently, we mistakenly use the requested device to get the
corresponding bluetooth route when try to transition state. While the
requeste bluetooth device address might be null so that this is only a
notification of a currently already connected device. Handle this
correctly to avoid further unexpected audio disconnection.

Bug: b/306113816
Test: atest BluetoothRouteManagerTest
Change-Id: I0dc5d8268d4ec495b4741fb17fb916547d0a7fdd