Remove all device from preference when BT is disabled

The issue is happened when BT is disabled then navigate to
"Connected devices". BluetoothDeviceUpdater didn't update
UI when BT is disabled. Remove all device from preference when
BT is disabled.

Bug: 80090956
Test: make -j42 RunSettingsRoboTests
Change-Id: Ia1fd8cfbcf95d712a1a702fdf101ff98186b76cd