Merge branch 'dz-bump-gitlab-shell' into 'master'

Bump gitlab-shell version to 4.0.0

New version includes https://gitlab.com/gitlab-org/gitlab-shell/merge_requests/102 and needed for https://gitlab.com/gitlab-org/gitlab-ce/issues/2772

See merge request !7200

GITLAB_SHELL_VERSION

-3.6.6
+4.0.0