Revert "[erp5_web_renderjs_ui] Use absolute wallpaper image URL to support firefox."

URL convertion has to be done by javascript so that the code become useable for officejs.

This reverts commit 9f8dd82c.

bt5/erp5_web_renderjs_ui/SkinTemplateItem/portal_skins/erp5_web_renderjs_ui/WebSection_renderDefaultPageAsGadget.py

 import json
 import re
-import urlparse
 
 if REQUEST is None:
   REQUEST = context.REQUEST
@@ -74,10 +73,6 @@ wallpaper_url = web_section.getLayoutProperty("configuration_wallpaper_url", def
 if wallpaper_url is None:
   mapping_dict["extra_css_full_link_tag"] = ''
 else:
-  if not urlparse.urlparse(wallpaper_url).scheme:
-    wallpaper_absolute_url = urlparse.urljoin(root_website_url+'/', wallpaper_url);
-  else:
-    wallpaper_absolute_url = wallpaper_url
   from base64 import urlsafe_b64encode
   mapping_dict["extra_css_full_link_tag"] = '<link rel="stylesheet" href="data:text/css;base64,%s">' % urlsafe_b64encode("""
   html::after {
@@ -94,6 +89,6 @@ else:
     background-attachment: fixed;
     background-image: url("%s");
   }
-  """ % wallpaper_absolute_url);
+  """ % wallpaper_url);
 
 return view_as_web_method(mapping_dict=mapping_dict)