AdapterService: Fix changing Active device from LeAudio headset

Don't stop playback when BluetoothAdapter service API is used to change active device,
because it means, there is another device which will continue on playing.
For this reason, when calling LeAudioService.removeActiveDevice API, the
hasFallbackDevice should be set to true to avoid audio stop.

Bug: 291071502
Test: atest ActiveDeviceManagerTest
Test: atest BluetoothInstrumentationTests
Test: 1. Manual change Acitve device while streaming from LE HS to speaker.
  2. Disconnect LE HS while streaming.
Tag: #feature
Change-Id: Id8b90ee1aaf712ef944450c2dc987dd993c3caab