The Owner permission for Group cannot be removed

Created by: Dan-stahr

What's wrong

Observed : I's impossible to "un-own" the user from a group. If you change an owner to someone else using the "Change Owner" button, the previous user still has the Owner permissions.

Expected : The Owner permissions should be either removed immediately on changing the owner or there should be a possibility to remove the permissions (at least by GitLab administrators) manually.

To reproduce :

Create a group G with user A as owner
Change owner of group G to user B
Change owner of the group back to user A
user B is still marked as owner and it's impossible to change his/her permissions

Info

GitLab version : 6.1.0 e4ba934 Config settings :

System information
System:     Debian 7.1
Current User:   git
Using RVM:  no
Ruby Version:   1.9.3p327
Gem Version:    1.8.23
Bundler Version:1.3.5
Rake Version:   10.1.0

GitLab information
Version:    6.1.0
Revision:   e4ba934
Directory:  /home/git/gitlab
DB Adapter: mysql2
URL:        my_url
HTTP Clone URL: my_url/some-project.git
SSH Clone URL:  git@my_url:some-project.git
Using LDAP: no
Using Omniauth: no

GitLab Shell
Version:    1.7.1
Repositories:   /home/git/repositories/
Hooks:      /home/git/gitlab-shell/hooks/
Git:        /usr/bin/git

AppCheck :

Checking Environment ...

Git configured for git user? ... yes
Has python2? ... yes
python2 is supported version? ... yes

Checking Environment ... Finished

Checking GitLab Shell ...

GitLab Shell version >= 1.7.0 ? ... OK (1.7.1)
Repo base directory exists? ... yes
Repo base directory is a symlink? ... no
Repo base owned by git:git? ... yes
Repo base access is drwxrws---? ... yes
update hook up-to-date? ... yes
update hooks in repos are links: ... 
... list of my repositories with OKs ... 

Checking GitLab Shell ... Finished

Checking Sidekiq ...

Running? ... yes

Checking Sidekiq ... Finished

Checking GitLab ...

Database config exists? ... yes
Database is SQLite ... no
All migrations up? ... yes
GitLab config exists? ... yes
GitLab config outdated? ... no
Log directory writable? ... yes
Tmp directory writable? ... yes
Init script exists? ... yes
Init script up-to-date? ... yes
Projects have satellites? ... 
... list of my repositories with yes's ...

Redis version >= 2.0.0? ... yes
Your git bin path is "/usr/bin/git"
Git version >= 1.7.10 ? ... yes (1.7.10)

Checking GitLab ... Finished