add a explicit interface for the home storage

lib/private/files/objectstore/homeobjectstorestorage.php

@@ -22,7 +22,7 @@ namespace OC\Files\ObjectStore;
 
 use OC\User\User;
 
-class HomeObjectStoreStorage extends ObjectStoreStorage {
+class HomeObjectStoreStorage extends ObjectStoreStorage implements \OCP\Files\IHomeStorage {
 
 	/**
 	 * The home user storage requires a user object to create a unique storage id

lib/private/files/storage/home.php

@@ -11,7 +11,7 @@ namespace OC\Files\Storage;
 /**
  * Specialized version of Local storage for home directory usage
  */
-class Home extends Local {
+class Home extends Local implements \OCP\Files\IHomeStorage {
 	/**
 	 * @var string
 	 */

lib/public/files/storage.php

@@ -336,3 +336,7 @@ interface Storage {
 	 */
 	public function instanceOfStorage($class);
 }
+
+interface IHomeStorage {
+
+}