MAGETWO-65589: [GitHub][PR] Update PurgeCache.php #8052

- fixed unit test for the added header and method call

Author: vrann

app/code/Magento/CacheInvalidate/Test/Unit/Model/PurgeCacheTest.php

@@ -70,7 +70,9 @@ public function testSendPurgeRequest($hosts)
                 ->with($uri->getHost(), $uri->getPort());
             $this->socketAdapterMock->expects($this->at($i++))
                 ->method('write')
-                ->with('PURGE', $uri, '1.1', ['X-Magento-Tags-Pattern' => 'tags']);
+                ->with('PURGE', $uri, '1.1', ['X-Magento-Tags-Pattern' => 'tags', 'Host' => $uri->getHost()]);
+            $this->socketAdapterMock->expects($this->at($i++))
+                ->method('read');
             $i++;
         }
         $this->socketAdapterMock->expects($this->exactly(count($uris)))