pkg/nimble/autoconn: stop scan/adv on NETIF_ABORT_SLAVE

When a connection is aborted and the node in question is a slave
then it can be advertising/scanning at the time. The incoming
event triggers the state to be changed to IDLE but ongoing adv/scan
which will cause 'nimble_netif_conn_start_adv' to fail to allocate
a handle as the netif will still be busy. Therefore when
stop scan/stop before switching the state.

pkg/nimble/autoconn/nimble_autoconn.c

@@ -215,7 +215,7 @@ static void _on_netif_evt(int handle, nimble_netif_event_t event,
             break;
         case NIMBLE_NETIF_ABORT_SLAVE:
             _evt_dbg("ABORT slave", handle, addr);
-            _state = STATE_IDLE;
+            _deactivate();
             break;
         case NIMBLE_NETIF_CONN_UPDATED:
             _evt_dbg("UPDATED", handle, addr);