Add a delay in master failover

I have seen some very seldom errors where (it seems) the address is
still live for a short while after removing it from the old master, thus
the new master will fail in startup/adding its own IP address.

To prevent against this, we add a delay/retry before we proceed, if the
IP is still reachable.

Signed-off-by: Iustin Pop <iustin@google.com>
Reviewed-by: René Nussbaumer <rn@google.com>
(cherry picked from commit 425f0f54)

Signed-off-by: Iustin Pop <iustin@google.com>
Reviewed-by: Balazs Lecz <leczb@google.com>