bug #16316 [FrameworkBundle] Fix ClassCacheWarme when classes.php is already warmed (tucksaun)

This PR was merged into the 2.8 branch.

Discussion
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[FrameworkBundle] Fix ClassCacheWarme when classes.php is already warmed

| Q             | A
| ------------- | ---
| Bug fix?      | yes
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | -
| License       | MIT
| Doc PR        | -

Autoreloading was previously set to `false`, but actually we want to force it.
This could even lead to a fatal error when warming where it was already warmed as the previous `classes.php` is directly required.

Commits
-------

d31350f [FrameworkBundle] Fix ClassCacheWarme when classes.php is already warmed

src/Symfony/Bundle/FrameworkBundle/CacheWarmer/ClassCacheCacheWarmer.php

@@ -34,6 +34,10 @@ class ClassCacheCacheWarmer implements CacheWarmerInterface
             return;
         }
 
+        if (file_exists($cacheDir.'/classes.php')) {
+            return;
+        }
+
         ClassCollectionLoader::load(include($classmap), $cacheDir, 'classes', false);
     }