[BUG] Healthchecks failing because of missing Curl

[sg3-141-592]

The current HEALTHCHECK is trying to use Curl.

HEALTHCHECK --interval=60s --start-interval=20s --timeout=3s \
  CMD curl -f http://localhost/ || exit 1

However Curl isn't available within the production layer, it's only installed into the build layer so containers always show can unhealthy.

I've worked around this by launching with a custom healthcheck command using Wget that is available in the production layer.

--health-cmd="wget --quiet --spider http://127.0.0.1:80 || exit 1"