minor #22224 Fix HttpCache test (chalasr)

This PR was merged into the 3.3-dev branch.

Discussion
----------

Fix HttpCache test

| Q             | A
| ------------- | ---
| Branch?       | master
| Bug fix?      | no
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | no
| Fixed tickets | https://github.com/symfony/symfony/pull/22043#discussion_r107864054
| License       | MIT
| Doc PR        | n/a

will make appveyor green.

Commits
-------

3178f50594 Fix failing HttpCache test on windows

src/Symfony/Component/HttpKernel/Tests/HttpCache/HttpCacheTest.php

@@ -564,6 +564,10 @@ class HttpCacheTest extends HttpCacheTestCase
 
     public function testDegradationWhenCacheLocked()
     {
+        if ('\\' === DIRECTORY_SEPARATOR) {
+            $this->markTestSkipped('Skips on windows to avoid permissions issues.');
+        }
+
         $this->cacheConfig['stale_while_revalidate'] = 10;
 
         // The prescence of Last-Modified makes this cacheable (because Response::isValidateable() then).