When we are no longer the natgw master, dont put the natgw ip on loopback.

When we are no longer the natgw master, dont put the natgw ip on loopback.
We put the ip on loopback just to make sure we would still interoperate with
non-standard configurations on unix-KDC, that are configured to verify the optional
HostAddresses field.
This is not required for AD, since AD does not use this field, and is replaced in
unix land with other/better mechanisms than this "dodgy" check.

This makes it "easier" for applications that have bound to the natgw address
to detect a socket problem and try to reconnect/recover if the ip address
is completely missing from the system.

At the same time, use the winbind specific hook that exists to explicitely tell winbindd : this address is gone, so if you have bound to it, this is a good time to close and rebind your socket.

cq 1020333