add health check to Dockerfile

Dockerfile

@@ -222,5 +222,10 @@ ARG SHBLOG=logs/shib-idp
 # Expose the port tomcat will be serving on
 EXPOSE 8443
 
+#establish a healthcheck command so that docker might know the container's true state
+HEALTHCHECK --interval=2m --timeout=30s \
+  CMD curl -k -f https://127.0.0.1:8443/idp/status || exit 1
+
+
 # Start tomcat/crond
 CMD ["/usr/bin/startup.sh"]