We use the built in python3 http server to bring up a temporary backend
on the node which wants to renew a certificate. The timeout set so that
the haproxy health check has noticed the backend come up before certbot
runs.
There is otherwise a race condition between the haproxy healthcheck and
the certbot challenge request arriving at the acme-challenge endpoint.
Change-Id: I2f5f9457c43c68f2881bf9d44f43434ca7b43859