bridge: Stop music on hold on adding an arbitrary channel to a bridge

When a channel that is on hold gets added to a bridge by
the Bridge AMI action or the dialplan application of the same name,
music continues to play, causing "robotic sound".

This commit adds a call to ast_moh_stop to stop the music.
Also, it makes the AMI Park action use the right MOH class when the
channel gets parked.

Reported by: Zane Conkle

ASTERISK-25079 #close

Change-Id: I4b129c5a20c15e63968842460ac5a1a85903cf9f