Change the initialization order of AvrcpTargetService

Create all necessary interfaces and initialize all variables before
registering for callbacks from other locations. This prevents different
interfaces from being null if an event takes place before initialization
is complete.

Bug: 111724742
Test: Sanity test with Carkit
Change-Id: I29efcf1d789fcda9178d08d65bfb10b50e79ff81