Fix support for testing exit code

The `$sectionData` was being overwritten, causing its assertion 
(`$this->assertSame()`) to fail.

tests/Composer/Test/AllFunctionalTest.php

@@ -183,6 +183,7 @@ class AllFunctionalTest extends TestCase
 
                 case 'EXPECT-EXIT-CODE':
                     $sectionData = (integer) $sectionData;
+                    break;
 
                 case 'EXPECT':
                 case 'EXPECT-REGEX':