Flush all received session callback events before attempting tear down

Some tests accumulate a lot of unhandled RangingEvents,
this is causing timeouts when attempting to deinit the session:
the tester spends too much time unqueuing them and timeouts before
getting the Closed event

Bug: 333463192
Test: atest CtsUwbMultiDeviceTestCase_FiraRangingTests:RangingTest#test_ranging_nearby_share_profile_bg_fails
Test: atest CtsUwbMultiDeviceTestCase_FiraRangingTests:RangingTest#test_ranging_nearby_share_profile_verify_app_in_bg_stops_session
Change-Id: I88dac5e1c77f7a56b67126faf85da8f8ec23d9c1
1 file changed