Automate acme.sh install-cert cmd

Summary:
This command have several opportunities to botch a certificate deployment,
e.g. if we miss fullchain, the daemon will still serve former certificate.

Automating it allows to apply correct pillar configuration, and maintain it.

Currently, this cmd.run isn't strictly equipollent, it will run this command
everytime, but the result on the server will be equipollent: same config,
same files content.

Fixes T2210.

Test Plan:

• Deploy to hervil
• Check the mail.nasqueron.org config have fullchain defined
• Check if the certificates files are correctly regenerated

Reviewers: dereckson

Reviewed By: dereckson

Maniphest Tasks: T2210

Differential Revision: https://devcentral.nasqueron.org/D3906