Cache map client state machine state

Problem: In certain situation(unknown), querying state machine to get
the current state results in index out of bound exception.

Solution: Cache the recent state in the map client state machine and
return the recent state rather than querying the state machine.

Test: atest GoogleBluetoothInstrumentationTests:com.android.bluetooth
        .mapclient.MapClientServiceTest
Test: atest GoogleBluetoothInstrumentationTests:com.android.bluetooth
        .mapclient.MapClientStateMachineTest
Test: Tested on messaging use-cases on seahawk.
Bug: 278023570
Tag: #stability
Change-Id: I9db80535da8bc31fa5ed48368743a9efe1a8819d