Healthchecks in elastic-docker-tls.yml always pass.

The current healthchecks, which look like this: `curl --cacert $CERTS_DIR/ca/ca.crt -s https://localhost:9200 >/dev/null; if [[ $$? == 52 ]]; then echo 0; else echo 1; fi`, pass even if a node is exposed on a port other than 9200, or if the node is not accessible for some reason. The echo commands both return a response code of 0.

Getting rid of the if statement fixes this, but we could also add logic to the healthcheck based on the http response code.