Fix cache in header.
should not set no-cache for RSS feeds since its purpose is to be consumed and cached
Merge branch '1972_fix_cache_in_header' into tuleap-stable-master

* 1972_fix_cache_in_header:
  should not set no-cache for RSS feeds since its purpose is to be consumed and cached
  Fix cache in header.
Tuleap 5.8.99.20