floss: Extend connect_audio for force_cvsd

Mainly added for verification purpose. This also provides a fallback
path for the audio stack to force CVSD if required.

Bug: 237314430
Tag: floss
Test: build deploy and verify by btmon and dbus-monitor with crrev/c/3872490
Change-Id: I19f4e348dfa1d06c8ea773da7e326a54677a0d3d