Use lowercase bdaddr and fix improper string compare in Volume Manager

Currently Bluetooth Native code uses lowercase Bluetooth addresses.
Instead have AvrcpNativeInterface.java convert these to uppercase since
this is what BluetoothDevice.java uses. This is so that the addresses
used by the volume manager will match in case. Also fix an improper
comparison in AvrcpVolumeManager.java.

Bug: 30602783
Test: See that Sony MDR-1RBT connects after being switched to the active
device and the remembered volume is correctly restored.

Change-Id: I84df84586d3d1ad846a9ff8e88bc28b772c0b87b