Log Message:
ruby-jirametrics: update to 2.4. Changes:

- The unit tests have never worked reliably on JRuby due to
  differences between JRuby and MRI (what we develop on). Fixed all
  the inconsistencies so that unit tests now work reliably on both MRI
  and JRuby.
- Fixed bug where blocked and stalled were not being reported correctly
  in some cases.
- In the (rare) case that jira redirects to a different URL, follow
  those redirects.