Restore .ssh/authorized_keys template

Summary:
The ssh_keys variable contains both information.

This is a follow-up for 105e8404727a and d22e55536d93e.

Test Plan: Tested with D2801

Reviewers: DorianWinty

Reviewed By: DorianWinty

Differential Revision: https://devcentral.nasqueron.org/D2804