minor #13738 [Security] Fix expectation in a test. (jakzal)

This PR was merged into the 2.6 branch.

Discussion
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[Security] Fix expectation in a test.

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

This is related to #13466, which worked perfectly fine in 2.3. It breaks in 2.6 since we've changed the way we check for master request.

Commits
-------

8299a44 [Security] Fix expectation in a test.

src/Symfony/Component/Security/Http/Tests/Firewall/ContextListenerTest.php

@@ -220,8 +220,8 @@ class ContextListenerTest extends \PHPUnit_Framework_TestCase
             ->will($this->returnValue(true));
 
         $event->expects($this->any())
-            ->method('getRequestType')
-            ->will($this->returnValue(HttpKernelInterface::MASTER_REQUEST));
+            ->method('isMasterRequest')
+            ->will($this->returnValue(true));
         $event->expects($this->any())
             ->method('getRequest')
             ->will($this->returnValue($request));