An auth external module requires ext_mod to be started first (#578)

src/ejabberd_app.erl

@@ -59,13 +59,13 @@ start(normal, _Args) ->
     ejabberd_rdbms:start(),
     ejabberd_riak_sup:start(),
     ejabberd_sm:start(),
-    ejabberd_auth:start(),
     cyrsasl:start(),
     % Profiling
     %ejabberd_debug:eprof_start(),
     %ejabberd_debug:fprof_start(),
     maybe_add_nameservers(),
     ext_mod:start(),
+    ejabberd_auth:start(),
     start_modules(),
     ejabberd_listener:start_listeners(),
     ?INFO_MSG("ejabberd ~s is started in the node ~p", [?VERSION, node()]),