Bluetooth: Mesh: Fix unable iv recovery 0 0 -> 1 0

According Mesh Spec 1.0.1:

Upon receiving and successfully authenticating to
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.

Look like test_iv_index.c:81
``` C

(bt_mesh_net_iv_update(TEST_IV_IDX + 1, BCN_IV_IN_IDLE));

```

This test case already exists, but the wrong testcase
to test wrong code.

Move `is_iv_recovery` into `bt_mesh_net_iv_update`.
First check whether it is IV recovery, and then carry out
the subsequent IV normal update procedure.

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