Clone staging repositories

Summary:
SSH access is required for private repository.

As such, the deploy user is granted an home directory
to store SSH files like known_hosts.

Test Plan:

• ensure repositories are well cloned on Ysul
• check permissions
• check submodules

Reviewers: dereckson

Reviewed By: dereckson

Differential Revision: https://devcentral.nasqueron.org/D1080