Commit c49f87313ad3d6c65d0a68c80763822772c42cbd, which added a vmute
option to the conference member flags, was somehow lost in the
mod_conference refactor. This commit restores the lost code.
FS-7813 #resolve
function name prefixes from shorthand 'conf' to longer form
'conference'. Also fixes the channel variable names which had been
caught in an over zealous perl -pi -e command...