cmd, docker: Updates for infrastructure

These are some changes to the relay pool server, upgrade server, and
crash receiver to run under Kubernetes. It's been in production for a
while.

script/strelaypoolsrv-entrypoint.sh

@@ -0,0 +1,10 @@
+#!/bin/sh
+
+set -eu
+
+if [ "$MAXMIND_KEY" != "" ] ; then
+	curl "https://download.maxmind.com/app/geoip_download?edition_id=GeoLite2-City&license_key=${MAXMIND_KEY}&suffix=tar.gz" \
+	| tar --strip-components 1 -zxv
+fi
+
+exec "$@"