Install PHP gettext extension everywhere

Summary:
As mentioned on T1932, ViMbAdmin requires the PHP gettext extension,
and we would like to get an unified set of extensions available
on the webserver-alkane, devserver and shellserver roles.

Test Plan: Deployed on WindRiver and web-001

Reviewers: dereckson

Reviewed By: dereckson

Differential Revision: https://devcentral.nasqueron.org/D3544