delete _remove roles from the run_list

When a `$barclamp-$role_remove` role (and its removal recipe) has successfully finished, delete it from the node's run_list.
No, sorry, I was wrong. What I thought was that the node's runlist contains the role, and it gets removed, but thats not the case - the runlist is empty even before we call ```delete_remove_role_from_runlist```. We're fine here. Sorry for the confusion.