Mount search to parent node of search form

Follow up to 5dee570cb2.

It seems the mount works slightly different in that it creates a div,
appends by the App element to the element you give it, after
clearing all it's child nodes.

The previous behaviour was that the old element was /replaced/
by the App element.

Bug: T296889
Change-Id: Iee7493c032f4de5389207bba288a1a70e4cd14f3

resources/skins.vector.search/skins.vector.search.js

@@ -35,7 +35,7 @@ function initApp( searchForm ) {
 		// Pass additional config from server.
 		}, config )
 	)
-		.mount( searchForm );
+		.mount( searchForm.parentNode );
 }
 /**
  * @param {Document} document