Add a flag to ./bin/worker to select tasks based on their failureCount
Summary:
I frequently run into a situation where I want to kill tasks that have accumulated a lot of failures regardless of what class they are. Or I'll want to kill every worker of a certain class but only if it has failed at least once. This change allows me to run `./bin/worker cancel --class <MYCLASS> --min-failure-count 5` to only kill tasks with at least 5 failed attempts.
The `--min-failure-count N` argument can be used by itself as well as with `--class CLASSNAME`. I don't think it makes sense for it to work with `--id ID`, but I'm not dead set on that or anything.
Test Plan: I ran the worker management workflow with and without the `--min-failure-count` argument and it worked as expected.
Reviewers: #blessed_reviewers, epriestley
Reviewed By: #blessed_reviewers, epriestley
Subscribers: Korvin, epriestley, yelirekim
Differential Revision: https://secure.phabricator.com/D16906