Setting the "use autoloader" switch to false on class_exists

We found this need because:
1. We do now have PHP_Invoker installed.
2. We have multiple autoloaders registered
3. When the class_exists was checking for "PHP_Invoker" it was
automatically trying to autoload it and failing in a way that fatally
ended our phpunit tests.

PHPUnit/Util/GlobalState.php

@@ -406,7 +406,7 @@ public static function phpunitFiles()
      */
     protected static function addDirectoryContainingClassToPHPUnitFilesList($className, $parent = 1)
     {
-        if (!class_exists($className)) {
+        if (!class_exists($className, false)) {
             return;
         }