Fixed RSS test case as per the new RSS header.
Fixed RSS test case as per the new RSS header.

inveniosoftware/invenio-search,tiborsimko/invenio-search,tiborsimko/invenio-records,inveniosoftware/invenio-records,inveniosoftware/invenio-search,inveniosoftware/invenio-records,tiborsimko/invenio-search,tiborsimko/invenio-records