minor #34225 [HttpFoundation] MockFileSessionStorageTest::sessionDir …

…being used after it's unset (HypeMC)

This PR was merged into the 3.4 branch.

Discussion
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[HttpFoundation] MockFileSessionStorageTest::sessionDir being used after it's unset

| Q             | A
| ------------- | ---
| Branch?       | 3.4
| Bug fix?      | yes
| New feature?  | no
| Deprecations? | no
| Tickets       | -
| License       | MIT
| Doc PR        | -

The `$sessionDir` property was used after being set to `null`.

Commits
-------

51b20dd Fix MockFileSessionStorageTest::sessionDir being used after it's unset

src/Symfony/Component/HttpFoundation/Tests/Session/Storage/MockFileSessionStorageTest.php

@@ -41,12 +41,12 @@ protected function setUp()
 
     protected function tearDown()
     {
-        $this->sessionDir = null;
-        $this->storage = null;
-        array_map('unlink', glob($this->sessionDir.'/*.session'));
+        array_map('unlink', glob($this->sessionDir.'/*'));
         if (is_dir($this->sessionDir)) {
             rmdir($this->sessionDir);
         }
+        $this->sessionDir = null;
+        $this->storage = null;
     }
 
     public function testStart()