conf: Remove <metadata> elements with no namespace

conf: Remove <metadata> elements with no namespace

Our docs state that subelements of <metadata> shall have a namespace
and the medatata APIs expect that too. To avoid inaccessible
<metadata> sub-elements, just remove those that don't conform to the
documentation.

Apart from adding the new condition this patch renames the function and
refactors the code flow to allow the changes.

Resolves: https://bugzilla.redhat.com/show_bug.cgi?id=1245525