Nest: fix bug in previous patches related to channel reconfiguration

The patch d506263d... blocked adding channel during reconfiguration,
that broke protocols which use the same functiona also during init.
This patch fixes that.

nest/proto.c

@@ -663,9 +663,13 @@ proto_configure_channel(struct proto *p, struct channel **pc, struct channel_con
   {
     /* We could add the channel, but currently it would just stay in down state
        until protocol is restarted, so it is better to force restart anyways. */
-    log(L_INFO "Cannot add channel %s.%s", p->name, cf->name);
-    return 0;
-    // *pc = proto_add_channel(p, cf);
+    if (p->proto_state != PS_DOWN)
+    {
+      log(L_INFO "Cannot add channel %s.%s", p->name, cf->name);
+      return 0;
+    }
+
+    *pc = proto_add_channel(p, cf);
   }
   else if (c && !cf)
   {