Merge pull request #8614 from axilleas/disable_check_all_issues_for_unprivileged_users

Disable 'check all issues' checkbox for unprivileged users.

app/views/projects/issues/_issues.html.haml

 .append-bottom-10
   .check-all-holder
-    = check_box_tag "check_all_issues", nil, false, class: "check_all_issues left"
+    = check_box_tag "check_all_issues", nil, false, class: "check_all_issues left", disabled: !can?(current_user, :modify_issue, @project)
   = render 'shared/issuable_filter'
 
   .clearfix