Update router id sequence number in router sync (#1594)

Router id sequence number updated in router sync to ensure that
the number will be updated in case of power cycling leader.

Author: Arto Kinnunen

source/6LoWPAN/Thread/thread_leader_service.c

@@ -1483,6 +1483,7 @@ void thread_leader_service_timer(protocol_interface_info_entry_t *cur, uint32_t
             thread_bootstrap_network_data_update(cur);
         }
     }
+
     if (cur->thread_info->leader_private_data->leader_id_seq_timer) {
         if (cur->thread_info->leader_private_data->leader_id_seq_timer > ticks) {
             cur->thread_info->leader_private_data->leader_id_seq_timer -= ticks;
@@ -1637,6 +1638,9 @@ int thread_leader_service_thread_partitition_restart(int8_t interface_id, mle_tl
     // Clear network data (if exists) and propagate new empty network data
     thread_network_data_free_and_clean(&cur->thread_info->networkDataStorage);
     thread_network_data_base_init(&cur->thread_info->networkDataStorage);
+    // Update router sequence id to prevent network fragmentation in case of Leader was temporarily down
+    // and routers were not able to get new sequence id for NETWORK_ID_TIMEOUT duration.
+    thread_leader_service_update_id_set(cur);
     return 0;
 }