Schedule mirror updates in parallel
Fixes https://gitlab.com/gitlab-org/gitlab-ee/issues/5034
Depends on (and includes) https://gitlab.com/gitlab-org/gitlab-ee/merge_requests/4723
/cc @tiagonbotelho
Edited by Douwe Maan
Fixes https://gitlab.com/gitlab-org/gitlab-ee/issues/5034
Depends on (and includes) https://gitlab.com/gitlab-org/gitlab-ee/merge_requests/4723
/cc @tiagonbotelho