Error when adding user to group where he is already assigned (#18665).

git-svn-id: http://svn.redmine.org/redmine/trunk@13785 e93f8b46-1217-0410-a6f0-8f06a7374b81
Fixed: LabelledFormBuilder#label outputs 2 label elements (#18679).

Patch by Masato NODA.

git-svn-id: http://svn.redmine.org/redmine/trunk@13786 e93f8b46-1217-0410-a6f0-8f06a7374b81