Fix: crmd: Prevent manual fencing confirmations from attempting to create node entries for unknown nodes

Otherwise "stonith_admin -C/--confirm" could add node entries for unknown nodes
Fix: crmd: Prevent message relay from attempting to create node entries for unknown nodes

Otherwise "crmadmin -S/--status" or "crmadmin -K/--kill" could add node
entries for unknown nodes
Merge pull request #427 from gao-yan/manual-ack-unknown-node

Fix: crmd: Prevent manual fencing confirmations from attemping to create node entries for unknown nodes