Medium: Shell: refine the node delete command

• don't try to remove the node if it's not in the CIB
• crm_node seems to return a wrong exit code, ignore that for the time being
• also, if the node is not reported by crm_node -l, it may be that it hasn't been around for a while, so we still proceed to remove it from the CIB
• more logging

Mercurial revision: c8a0da78ada88e0c56e7115444941457b95ad5ca