[LE audio Unicast]To clear the SetMemberPair when BT is turning off

Since the device's bond state got stuck at BOND_BONDING, it caused the
settings can't connect the member device. It can't recover by airplane
mode or restarting the BT.
Here resets the flag for recovery. To clear the SetMemberPair flag
when the Bluetooth is turning off.

Bug: 240380931
Test: build pass.
[pass] make RunSettingsLibRoboTests -j40 ROBOTEST_FILTER=CachedBluetoothDeviceManagerTest

Change-Id: I6b6ed2537b35be99c5c61749d2ab3ee1d2c35510