Upgrade devserver and shellserver roles to PHP 7.2
Summary:
PHP 7.2 reaches both FreeBSD and Debian Sid packages.
We can so migrate from PHP 7.1 to PHP 7.2 dev/shell servers.
Test Plan: dereckson
Reviewers: dereckson
Reviewed By: dereckson
Differential Revision: https://devcentral.nasqueron.org/D1362