Bluetooth: Mesh: Fix iv recovery unable clear replay list

When local node enter iv recovery procedure, should clear
replay list at first due to avoid possible wrong replay attack.

At present, `bt_mesh_rpl_clear` schedule a timer to clear rpl,
this would cause local node unable precess mesh message(IV Updated).

Also, in `bt_mesh_rpl_pending_store` also not clear rpl, which check
`BT_MESH_VALID` flag, always valid for iv recovery.

So, Add `rpl_clear_pending` work handler process rpl clear.

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