floss: Support using VGS to set HF volume

Append the Bluetooth address parameter for SetVolume DBus message so the
audio client can use it to set HFP device's speaker volume.

Bug: 229748367
Tag: #floss
Test: build, deploy, connect and test by sending DBus message
BYPASS_LONG_LINES_REASON: Bluetooth likes 120 char lines

Change-Id: I39c87f41b25d3b684ef0c7bf4a04107390514fcd