When the connection becomes invisible to a user (ie, the permissions
of the connection no longer allow that user to view the connection)
then we have to hid the connection from clients. But we can't
just dispose of it, because visibility changes are signaled with
Update signals on the connection itself, and thus we need to keep
the connection around just in case it becomes visible to the user
again. But if it's invisible, make sure we clear out the settings
since they may have changed.
