fix grabRepository logic (#58)

Author: TavoNiievez

src/Codeception/Module/Symfony.php

@@ -1290,14 +1290,14 @@ public function grabRepository($mixed)
             return $repo;
         };
 
-        if (interface_exists($mixed)) {
-            return $getRepo();
-        }
-
         if (is_object($mixed)) {
             $mixed = get_class($mixed);
         }
 
+        if (interface_exists($mixed)) {
+            return $getRepo();
+        }
+
         if (!is_string($mixed) || !class_exists($mixed) ) {
             $isNotARepo();
             return null;