ctdb-daemon: Check if updates are in flight when releasing all IPs

ctdb-daemon: Check if updates are in flight when releasing all IPs

Some code involved in releasing IPs is not re-entrant.  Memory
corruption can occur if, for example, overlapping attempts are made to
ban a node.  We haven't been able to recreate the corruption but this
should protect against it.

Signed-off-by: Martin Schwenke <martin@meltin.net>
Reviewed-by: Amitay Isaacs <amitay@gmail.com>