leaudio: Improve active device handling

Make sure that intent ACTION_LE_AUDIO_ACTIVE_DEVICE_CHANGED is sent only
when devices has changed.

Bug: 150670922
Tag: #feature
Sponsor: jpawlowski@
Test: atest BluetoothInstrumentationTests
Change-Id: I3bf6ab37ecae06d562e825d248467f740d7d2893
1 file changed