Eventscripts - 10.interfaces should not check orphaned interfaces.

Eventscripts - 10.interfaces should not check orphaned interfaces.

If the last IP address on an interfaces is removed then that
interfaces should no longer be checked by 10.interfaces.  However,
"ctdb ifaces" still lists such interfaces so they are currently
checked.

The problem really needs to be addressed in ctdbd but a neat quick
eventscript fix will be minimally invasive...

This changes the code to use "ctdb -Y ip -v" instead of "ctdb -Y
ifaces".  The former includes details of all public addresses and
associated interfaces, so when an address is removed there is no
output for it.  This avoids orphaned interfaces from being listed.

The logic is also slightly improved so that $IFACES includes just a
(non-uniquified) list of interfaces, allowing an existing loop to be
removed.

Signed-off-by: Martin Schwenke <martin@meltin.net>