Switch Manager should ignore redundant updates

- Redundant node and node connector updates (such as in the case of
  cluster switchover) should not be notified to apps/listeners, to avoid expensive tasks

Change-Id: Ia541bdcba6b53170c7a6c29e2c35f1b7b8104d60
Signed-off-by: Yevgeny Khodorkovsky <ykhodork@cisco.com>