Provision jails

Summary:
On FreeBSD servers, we can use jails to divide processes.

This change installs ezjail and configure rc.

Logic to prepare the list of jails from the pillar
is handled by a custom execution module, to avoid
code in jinja templates.

Test Plan:

• ezjail-admin can be used
• /etc/rc.conf.d/jail contains the list of jails
• flake8 _modules/jails.py | grep -v F821 doesn't return any issue (F821 is the undefined name issue, for pillar and grains)

Reviewers: dereckson

Reviewed By: dereckson

Differential Revision: https://devcentral.nasqueron.org/D1089