Inform AudioManager if absolute volume is supported after connection

Previously we were setting the absolute volume flag in audio manager
before disconnecting the previous active device and connecting the next
active device. This led to absolute volume somtimes falsly being
reported as unsupported due to the fact that the Audio Service clears
the flag while disconnecting the previous A2DP device. By waiting for
the new device to inform the Audio Service that the remote device
supports absolute volume.

Bug: 79504164
Test: Switch between devices that support absolute volume
Change-Id: I56ddc55c8343ba562e964d8664d61649290e7443