unbound header is out of order with concat setup

it appears that the first concat::fragment must not occur in before the
first call to concat itself.
This is what issues the call to concat::setup, without which we don't
know in which directory to place the header's fragment file.
concat::fragment will attempt to place it into

  /_etc_unbound_unbound.conf/fragments/00_unbound-header
Merge pull request #35 from igalic/concat-order

unbound header is out of order with concat setup