Geo: Fix metrics updates when secondary nodes are cached
Due to https://gitlab.com/gitlab-org/gitlab-ee/merge_requests/8802,
Gitlab::Geo.secondary_nodes
can return an Array instead of an
ActiveRecord relation if the value is retrieved from the cache.
Fix this by using each
instead of find_each
, since loading a few
GeoNode records into memory shouldn't be a big deal.
Closes #9000 (closed)