userportal: Fix url-pattern for GwtCachingFilter

This patch fixes wrong url-pattern for GwtCachingFilter,
so that UserPortal resources have proper caching policies
applied via this filter.

Change-Id: I7f40e41ca17bdb9870b60d112af8f12bab82e6e9
Bug-Url: https://bugzilla.redhat.com/875814
Signed-off-by: Vojtech Szocs <vszocs@redhat.com>