ctdb-tests: Need to drop public IPs in kill-failover tests

ctdb-tests: Need to drop public IPs in kill-failover tests

These tests simulate a dead node rather than a CTDB failure, so drop
IP addresses when killing a "node" to avoid problems with duplicates.

To cope with a CTDB failure a watchdog would be needed to ensure that
the public IPs are dropped when CTDB dies.  Let's not do that now.

Signed-off-by: Martin Schwenke <martin@meltin.net>
Reviewed-by: Amitay Isaacs <amitay@gmail.com>
Autobuild-User(master): Martin Schwenke <martins@samba.org>
Autobuild-Date(master): Fri Dec  5 23:29:39 CET 2014 on sn-devel-104