`FLATNOTES_PORT` is not documented an conflicts with the kubernetes default environment variable assignment

[sparksis]

Given a services resource named flatnotes kubernetes will create and automatically inject an environment variable FLATNOTES_PORT=tcp://10.152.183.133:80 into all containers within the namespace. This conflicts with these.

Given that the services resource port does not necessarily align with the contain port the best solution may be to skip processing that portion of the script in entrypoint.sh if KUBERNETES_PORT is not empty ([[ -z "${KUBERNETES_PORT}" ]]).

I think it would also be valuable to document the existence and usage of FLATNOTES_PORT.