Source healthcheck endpoint from build argument

[shrink]

Default to the naive http://127.0.0.1:8080/.container/status healthcheck endpoint but support the ability to pass in another at build time.

Also, consider configurability of the retries and timeout -- what are defaults used in other images? Do the current defaults make sense?

[shrink]

The custom healthcheck endpoint should be included in the list of paths not included in the access log.