Low: attrd: delay lrmd connect until needed

Before, for each attribute change, we would attempt to connect to the lrmd,
then send any alerts. However, most clusters won't have attribute alerts,
so the connection is unnecessary. Now, attrd waits until the connection
is actually needed before attempting to connect.

This also removes obsolete handling from the lrmd callback, since the
lrmd no longer notifies clients of alert completion.