Fixes #20544 - Make CSS assets findable to sprockets

Without using the proper extension, new versions of sass + sprockets
won't compile assets.
It will simply not find the assets because they don't have the right
extension. Also, we have to add the stylesheet assets to sprockets paths
- which was done automatically before.

app/assets/stylesheets/katello/katello.scss

@@ -1,3 +1,10 @@
+/**
+ * = require "katello/jquery.loadmask.css"
+ * = require "katello/jquery-ui-1.8.11.custom.css"
+ * = require "katello/jquery.treeTable.css"
+ * = require "katello/ui.spinner.css"
+ */
+
 @import "katello/overrides";
 @import "katello/katello_base";
 @import "katello/look";
@@ -7,11 +14,6 @@
 @import "katello/widgets/tabs";
 @import "katello/katello_sprites";
 
-@import "katello/jquery.loadmask";
-@import "katello/jquery-ui-1.8.11.custom";
-@import "katello/jquery.treeTable";
-@import "katello/ui.spinner";
-
 @import "katello/contents";
 @import "katello/generic";
 @import "katello/notifications";