Bluetooth: Mesh: Fix unable iv recovery when in iv update state

According Mesh Profile 3.10.6 IV Index Recovery procedure

Upon receiving and successfully authenticating a Secure Network
beacon for a primary subnet whose IV Index is 1 or more higher
than the current known IV Index, the node shall set its current
IV Index and its current IV Update procedure state from the
values in this Secure Network beacon.

Signed-off-by: Lingao Meng <menglingao@xiaomi.com>