Bluetooth: Mesh: Discard iv update 1 0 --> 1 1

According spec, for the same iv index, iv update flag
should trans to false, when iv update procedure complete.

When local environment has attack-node
to store old network beacon(1,1), and re-send same
network beacon(1,1) after 192hours, will cause whole
bluetooth mesh network broke.

Signed-off-by: Lingao Meng <menglingao@xiaomi.com>
(cherry picked from commit 75cfa344)