removing cluster member (WIP)

Remove node from a cluster. See https://trello.com/c/xarZEs6g/846-ha-support-removing-nodes-from-clusters

https://github.com/crowbar/barclamp-crowbar/pull/1011 (or its roxy version) is needed so the remove role get correctly deleted after it is used once.
Does `crm node status` return exit code 0 if the node exists, or if it's online?