fix ceph-mon -> ceph-mon-tools -> ceph-mon circular dependency

fix ocaml-ocamlbuild -> ocaml-ocamlbuild circular dependency

fixes typo introduced in commit 2a307f3880b9 (community/nextcloud: main
packages provides also subpkg settings, 2020-05-01)

ref #11392

remove -postgresql subpackage which only tried to pull in non-existing
py-psycopg2 dependency, while py3-psycopg2 was explicitly installed by
main package.

also make the install_if for nginx uwsgi include the exact version of
patchwork to avoid chaos in case multiple versions of patchwork exists
in repository.