Check for the AD disabled flag in Access#allowed?

lib/gitlab/ldap/access.rb

@@ -14,7 +14,11 @@ module Gitlab
       end
       def allowed?(user)
-        !!Gitlab::LDAP::Person.find_by_dn(user.extern_uid, adapter)
+        if Gitlab::LDAP::Person.find_by_dn(user.extern_uid, adapter)
+          !Gitlab::LDAP::Person.ad_disabled?(user.extern_uid, adapter)
+        else
+          false
+        end
       rescue
         false
       end