RDS: don't update ip address tables if the address hasn't changed

If the ip address tables hasn't changed, there is no need to remove
them only to be added back again.

Lets fix it.
Reviewed-by: Ajaykumar Hotchandani <ajaykumar.hotchandani@oracle.com>
Signed-off-by: Santosh Shilimkar <ssantosh@kernel.org>
Signed-off-by: Santosh Shilimkar <santosh.shilimkar@oracle.com>
Signed-off-by: David S. Miller <davem@davemloft.net>