bin/main: Print usage when no command given

Minor regression from https://github.com/ostreedev/ostree/pull/1106. We
want to print the usage text both when unknown commands are passed, as
well as when no commands are passed at all.

Closes: #1126
Approved by: cgwalters

src/ostree/ot-main.c

@@ -181,10 +181,10 @@ ostree_run (int    argc,
             {
               g_set_error (&error, G_IO_ERROR, G_IO_ERROR_FAILED,
                            "Unknown command '%s'", command_name);
-              ostree_usage (commands, TRUE);
             }
         }
 
+      ostree_usage (commands, TRUE);
       goto out;
     }