Fix deadlock in LocalBluetoothManager

Following deadlock exist in previous code:
1. Main thread
Device.refresh()->Device.dispatchCallback()->Lock callback->(handle
callback in systemui)->DeviceManager.getDevicesCopy()-> try lock
deviceManager
2. Bg thread
DeviceManager.onUuidChange()->Lock
deviceManager->Device.refresh()->Device.dispatchCallback()-> try lock
callback

This CL remove sychnorized method in DeviceManager to unblock this
deadlock. Since UuidChange can only happen in bg thread, we don't need
this extra lock in DeviceManager.

Fixes: 112483982
Test: Manual
Change-Id: I1a8bb130cfff40358783f5f5da7e50e5f0a42e20