MAGETWO-93497: admin/url/custom cause media directives to break

- Added integration test cover

Author: dyushkin

dev/tests/integration/testsuite/Magento/Cms/Helper/Wysiwyg/ImagesTest.php

@@ -7,6 +7,9 @@
 
 use Magento\Framework\App\Filesystem\DirectoryList;
 
+/**
+ * @magentoAppArea adminhtml
+ */
 class ImagesTest extends \PHPUnit\Framework\TestCase
 {
     public function testGetStorageRoot()
@@ -23,6 +26,12 @@ public function testGetStorageRoot()
         $this->assertStringStartsWith($mediaPath, $helper->getStorageRoot());
     }
 
+    /**
+     * @magentoConfigFixture default_store admin/url/use_custom 1
+     * @magentoConfigFixture default_store admin/url/custom http://backend/
+     * @magentoConfigFixture admin_store web/secure/base_url http://backend/
+     * @magentoConfigFixture admin_store web/unsecure/base_url http://backend/
+     */
     public function testGetCurrentUrl()
     {
         $helper = \Magento\TestFramework\Helper\Bootstrap::getObjectManager()->create(