Fix UI incorrect when switch active device to hearing aid

When active device change to Hearing Aid,
BluetoothEventManager also send onActiveDeviceChanged() to notify
that active device of A2DP profile is null. To handle this case,
check hearing aid device is active device or not. If Hearing aid
device is active device then return Hearing aid device id,
otherwise return phone device id.

Bug: 128956186
Test: RunSettingsLibRoboTests
Change-Id: I1ba9249d7a7f634b56df019450643cfe147a5fb8