Allow worker tasks to be cancelled by classname
Summary:
Ref T3554. Makes `bin/worker cancel --class <classname>` work (cancel all tasks with that type).
This is useful in development if your queue is full of a bunch of gunk, and a need has occasionally arisen in production environments (usually "one option is cancel everything and move on").
Test Plan: Ran `bin/worker cancel` to cancel blocks of tasks by class name.
Reviewers: chad
Reviewed By: chad
Maniphest Tasks: T3554
Differential Revision: https://secure.phabricator.com/D16267