Merge pull request #5400 from lokedhs/master

When looking up a user by DN, use single scope

lib/gitlab/ldap/user.rb

@@ -78,7 +78,7 @@ module Gitlab
         # * when ldap account was deactivated by change of OU membership in 'dn'
         def blocked?(dn)
           ldap = OmniAuth::LDAP::Adaptor.new(ldap_conf)
-          ldap.connection.search(base: dn, size: 1).blank?
+          ldap.connection.search(base: dn, scope: Net::LDAP::SearchScope_BaseObject, size: 1).blank?
         end
 
         private