Immediately delete a floating IP if doesn't attach

When floating IPs fail to attach to nodes nodepool leaks that floating
IP. Correct this by immediately removing the floating IP as we have the
IPs id after creation but not during cleanupServer (because the floating
IP was never associated to any server).

Closes-Bug: #1301111
Change-Id: Ib6460797a8d9b31b1ad723e056dbfe6d57438bf7