A2dpService: provide Adapter in constructor

Test will no longer rely on AdapterService.getAdapterService and no
longer crash all the other test when failing.
Also the provided adapter will no longer be cleared and will be always
valid for the lifetime of the test

Bug: 321202011
Test: atest A2dpServiceTest
Flag: Exempt, changing parameter order initialization & test only
Change-Id: I7577d0920d52a591153a764544c93a7b497b5768