Update user.php

Fixes $_setupedBackends[] into self::$_setupedBackends[] so that setuped backends are REALLY remembered and not instanciated many times.

lib/user.php

@@ -190,7 +190,7 @@ class OC_User {
 					// use Reflection to create a new instance, using the $args
 					$backend = $reflectionObj->newInstanceArgs($arguments);
 					self::useBackend($backend);
-					$_setupedBackends[] = $i;
+					self::$_setupedBackends[] = $i;
 				} else {
 					OC_Log::write('core', 'User backend ' . $class . ' already initialized.', OC_Log::DEBUG);
 				}