Create ZFS filesystem for /datacube on devserver

Summary:
Devserver uses /datacube for arbitrary directories,
for example to serve Git repositories.

On a VM, it's intended to be used to a separate disk than /.
On baremetal, it lives on the same raid of disks than /.

Ref T1537.

Test Plan: Deploy on WindRiver

Reviewers: dereckson

Reviewed By: dereckson

Maniphest Tasks: T1537

Differential Revision: https://devcentral.nasqueron.org/D3059