Add pre/post renewal hooks scripts

[dongbohu]

This PR adds pre and post renewal scripts so that the SSL certificate can be renewed successfully. The pre script stops neo4j docker container before renewal process (otherwise port 80 would be taken by the docker container and the renewal would fail); and post scripts starts the docker container.

[dongbohu]

@dhimmel: I have tested the new scripts and renewed the SSL certificate on https://neo4j.het.io successfully.

[dhimmel]

So guessing that without this renewal has been failing? If we have any logs of the failure can we post them as a PR comment so we can search for them in the future if something similar happens.

One minor suggestion, otherwise looks good to me. I will merge when ready.

[dhimmel]

Suggested change

	# This script will be executed ONLY WHEN certificate is renrewed successfully.
	# This script will be executed ONLY WHEN certificate is renewed successfully.

[dongbohu]

Good catch. Thanks.

[dhimmel]

So the command above is just for the initial installation of SSH and the hooks are for future renewals?

[dongbohu]

Yes.

[dongbohu]

@dhimmel: I realized this issue due to a message sent to team-contact channel in Slack. You can take a look at that message (and my reply).

The exact error can be found in /var/log/letsencrypt/letsencrypt.log*. It is kind of esoteric and tedious. Here is part of it:

2019-07-01 22:49:30,323:INFO:certbot.auth_handler:Performing the following challenges:
2019-07-01 22:49:30,323:INFO:certbot.auth_handler:http-01 challenge for neo4j.het.io
2019-07-01 22:49:30,324:DEBUG:acme.standalone:Failed to bind to :80 using IPv6
2019-07-01 22:49:30,324:DEBUG:acme.standalone:Failed to bind to :80 using IPv4
2019-07-01 22:49:30,324:DEBUG:certbot.error_handler:Encountered exception:
Traceback (most recent call last):
  File "/usr/lib/python3/dist-packages/certbot/plugins/standalone.py", line 76, in run
    address, self.http_01_resources)
  File "/usr/lib/python3/dist-packages/acme/standalone.py", line 189, in __init__
    BaseDualNetworkedServers.__init__(self, HTTP01Server, *args, **kwargs)
  File "/usr/lib/python3/dist-packages/acme/standalone.py", line 108, in __init__
    raise socket.error("Could not bind to IPv4 or IPv6.")
OSError: Could not bind to IPv4 or IPv6.

[dongbohu]

If you don't have any other comments, please feel free to merge it. Thanks.