leaudio: Do not update local metadata if not needed

local_metadata_context_types_ should be updated only on MetadataUpdate
event. This will fix the problem, when offloader is changing source
metadata to converational and then back to media.
Without this patch, when context is changed to media, on the sink path
we still would keep conversational, which might afect future
configuration

Bug: 367894783
Bug: 352686917
Test: atest bluetooth_le_audio_client_test
Flag: com.android.bluetooth.flags.leaudio_speed_up_reconfiguration_between_call

Change-Id: I4a560ce73e49116df4f0179fd71592443ab50558