Updates to the curater container.

- Update version of elasticsearch-curator.
- Update version of Alpine linux.
- Use supersonic instead of crond.

curator/Dockerfile

-FROM python:3.7-alpine
-RUN pip install --progress-bar=off --no-cache-dir elasticsearch-curator==5.5.4
-COPY --chown=root:root entrypoint /
-ENTRYPOINT [ "/entrypoint" ]
-CMD [ "/usr/sbin/crond", "-fd7" ]
-HEALTHCHECK --timeout=1s CMD pgrep crond || exit 1
+FROM adarnimrod/cron as supersonic
+
+FROM python:3.7-alpine3.9
+COPY --from=supersonic /usr/local/bin/supersonic /usr/local/bin/
+RUN pip install --progress-bar=off --no-cache-dir elasticsearch-curator==5.7.6
+USER nobody
+CMD [ "supersonic", "/etc/crontabs/nobody" ]
+HEALTHCHECK --timeout=1s CMD pgrep supersonic || exit 1