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

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extra : convert_revision : svn%3Ae93f8b46-1217-0410-a6f0-8f06a7374b81/trunk%4012924
prevent issue tree hierarchy is broken in race conditions (#6579)

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

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extra : convert_revision : svn%3Ae93f8b46-1217-0410-a6f0-8f06a7374b81/trunk%4012927
Removed hard-coded strings (#16164).

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extra : convert_revision : svn%3Ae93f8b46-1217-0410-a6f0-8f06a7374b81/trunk%4012928