Bulk edit workflows for multiple trackers/roles (#16164).

git-svn-id: http://svn.redmine.org/redmine/trunk@12924 e93f8b46-1217-0410-a6f0-8f06a7374b81
prevent issue tree hierarchy is broken in race conditions (#6579)

awesome_nested_set 2.1.6 uses lock.
Issue model uses as same way.

git-svn-id: http://svn.redmine.org/redmine/trunk@12927 e93f8b46-1217-0410-a6f0-8f06a7374b81