session CHANGE server ctx locking

Also some other bugfixes.
diff --git a/src/messages_client.c b/src/messages_client.c
index d6ec444..c53658a 100644
--- a/src/messages_client.c
+++ b/src/messages_client.c
@@ -678,7 +678,7 @@
 
     case NC_RPL_NOTIF:
         nc_notif_free((struct nc_notif *)reply);
-        break;
+        return;
     }
 
     free(reply);