Raise the ConfBridgeMute/Unmute events when a CLI or AMI action triggers the change

New in 12 are the ConfBridgeMute/Unmute events, which are triggered when a user
changes their mute/unmute state. This was typically triggered when a user hit a
DTMF key that triggered the mute/unmute menu handler. Forgotten in this is when an
AMI action or CLI command triggers the mute/unmute. This patch now raises the
events in those situations as well.

(closes issue ASTERISK-21802)
Reported by: Birger "WIMPy" Harzenetter

git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@389402 65c4cc65-6c06-0410-ace0-fbb531ad65f3