subgroup owner cannot create milestones

Summary

When a user is defined as a member of a subgroup and not the group, he/she is unable to create milestones or even see milestones

Steps to reproduce

  • assign a user as an owner of a group
  • define some milestones - these milestones will be available to that user to view, delete, assign to issues. That user will also be able to create milestones
  • remove that member from the group and add that user as an owner of a subgroup (this is needed if you want to restrict that user to only see the contents of the subgroup)
  • that user will no longer be able (even as a subgroup owner) to create milestones but also view existing milestones and update issues with milestones

Example Project

This is not linked to a project but can be reproduced on our environment. https://gitlab.com/globalgig-inc/test-subgroup can be used for testing and reproduction.

What is the current bug behavior?

as a subgroup owner, I am unable to create milestones or assign issues to milestones

What is the expected correct behavior?

as a subgroup owner, I should be able to create milestones for my issues, assign my issues to existing milestones so they roll up into the group's board

Relevant logs and/or screenshots

(Paste any relevant logs - please use code blocks (```) to format console output, logs, and code as it's tough to read otherwise.)

Output of checks

(If you are reporting a bug on GitLab.com, write: This bug happens on GitLab.com)

Results of GitLab environment info

Expand for output related to GitLab environment info 
(For installations with omnibus-gitlab package run and paste the output of:
`sudo gitlab-rake gitlab:env:info`)

(For installations from source run and paste the output of:
`sudo -u git -H bundle exec rake gitlab:env:info RAILS_ENV=production`)

Results of GitLab application Check

Expand for output related to the GitLab application check 
(For installations with omnibus-gitlab package run and paste the output of:
sudo gitlab-rake gitlab:check SANITIZE=true)


(For installations from source run and paste the output of:
sudo -u git -H bundle exec rake gitlab:check RAILS_ENV=production SANITIZE=true)


(we will only investigate if the tests are passing)

Possible fixes

(If you can, link to the line of code that might be responsible for the problem)