recoverd: Clear IP assignment tree on election loss

recoverd: Clear IP assignment tree on election loss

If a node was previously recovery master (say, 20 years ago) and it
becomes recovery master again then, if IP assignments have changed,
verify_remote_ip_allocation() can produce messages like the following
when called during recovery:

  ctdbd: recoverd:Inconsistent IP allocation - node 0 thinks 10.1.1.1 is held by node 0 while it is assigned to node 1

When a node loses an election it should clear all data specific to it
being the recovery master.

Signed-off-by: Martin Schwenke <martin@meltin.net>
Reviewed-by: Amitay Isaacs <amitay@gmail.com>
(Imported from commit b234ae0a900052b03ca22efab8fa1b9e11f44ecc)