Fix backoffice breaking when Actions use code in their JsSource - U4-6843

This reverts/refactors this pull request: https://github.com/umbraco/Umbraco-CMS/pull/722/files

Since JsSource can be used for a file path or actual javascript, we can't use IOHelper.ResolveUrl here.  Instead we're moving it to the GetLegacyActionJs() method, which already handles deciding if it's a code or a URL.

💩

Conflicts:
	src/umbraco.cms/Actions/Action.cs

src/Umbraco.Web/Editors/BackOfficeController.cs

@@ -475,7 +475,7 @@ namespace Umbraco.Web.Editors
                     if (isValid)
                     {
                         //it is a valid URL add to Url list
-                        urlList.Add(jsFile);
+                        urlList.Add(IOHelper.ResolveUrl(jsFile));
                     }
                 }
                 else

src/umbraco.cms/Actions/Action.cs

@@ -89,7 +89,7 @@ namespace umbraco.BusinessLogic.Actions
         {
         	return ActionsResolver.Current.Actions
 				.Where(x => !string.IsNullOrWhiteSpace(x.JsSource))
-                .Select(x => IOHelper.ResolveUrl(x.JsSource)).ToList();
+                .Select(x => x.JsSource).ToList();
         	//return ActionJsReference;
         }