Ensure that crowd healthcheck returns a 200 instead of a 204

At the moment Crowd's healthcheck returns a 204 http status code which is not compatible with most of the Load Balancers. Changes are being made on the healthcheck library[1] to ensure that we can return a 200 status code so crowd can be used behind AWS ELB.

[1]: https://bitbucket.org/atlassian/atlassian-healthcheck/pull-requests/33/ahc-43-add-an-optional-parameter-to-use-an/diff