Provision /etc/resolv.conf to jails

Summary:
Files added to /usr/jails/newjail are automatically provisionned
to new jails.

DNS picked are Level 3 and Google.

Test Plan: Provision a new jail, check DNS works inside of it

Reviewers: dereckson

Reviewed By: dereckson

Differential Revision: https://devcentral.nasqueron.org/D1094