MapClient clean up at start

Clean up stale data if an unexpeced shutdown occurs while devices are
connected.
Bug: 181696727
Bug: 189207206
Test: atest BluetoothInstrumentationTests
Tag: #stability

Change-Id: I15a0b54b963591e2df87657cc3a1dae0949374f0
Merged-In: I15a0b54b963591e2df87657cc3a1dae0949374f0