ProfileService: Inline do{Start,Stop}

Inline the doStart and doStop inside AdapterService,
allowing to remove multiple null checks as it's
not possible (as it's not async anymore) for
the AdapterService to be null.

Bug: 319112725
Test: m Bluetooth BluetoothInstrumentationTests
Flag: Exempt, mechanical refactor
Change-Id: I40b39f523808ba6c06e0527103f844705a7f19ed