Ensure group/project owners can see their members' access_level

When you are the last owner of a group or the owner of a project,
you don't have the :update_<source>_member / :destroy_<source>_member
abilities, but you do have the :admin_<source>_member so you should
be able to see your members access levels.

Signed-off-by: Rémy Coutable <remy@rymai.me>