HeadsetTest: localAdapter & not depend on intent

instead of relying on intent being sent and received, directly check the
context to see what is ask to be sent

Bug: 338303046
Test: atest HeadsetServiceAndStateMachineTest
Test: atest HeadsetServiceTest
Flag: Exempt, test only
Change-Id: I5d5ce45a0190bd41b7967cd9a8074b035cdb524a