le_audio: Queue broadcast when unicast is getting active

Missing check of getting active group cause broadcast not caching. Not
caching broadcast implies in queuing this in native and not informing
unicast about request to handover.

Tag: #Bug
Bug: 332847049
Test: atest LeAudioServiceTest LeAudioBroadcastServiceTest
Flag: Exempt, trivial fix
Change-Id: Ifa792559ef52901fc4eaaca58ee9e5aae0019103