MXS-1220: Add execution of module commands to REST API

The module command self links now point to an endpoint that executes the
module command. Depending on the type of the module command, either a GET
or a POST request must be made.

server/modules/routing/avrorouter/avro.c

@@ -148,7 +148,7 @@ MXS_MODULE* MXS_CREATE_MODULE()
         { MODULECMD_ARG_SERVICE | MODULECMD_ARG_NAME_MATCHES_DOMAIN, "The avrorouter service" },
         { MODULECMD_ARG_STRING, "Action, whether to 'start' or 'stop' the conversion process" }
     };
-    modulecmd_register_command(MXS_MODULE_NAME, "convert", avro_handle_convert, 2, args);
+    modulecmd_register_command(MXS_MODULE_NAME, "convert", MODULECMD_TYPE_ACTIVE, avro_handle_convert, 2, args);
 
     static MXS_ROUTER_OBJECT MyObject =
     {