Allow to recreate Vault configuration as DRP plan B

Summary:
If Vault has any issue, we can spin a new node with the storage backend
as disaster recovery plan A. If that storage backend is lost, the unit
vault/bootstrap contains instructions to recreate the configuration,
mainly the engines configuration.

Ref T1702

Reviewers: dereckson

Reviewed By: dereckson

Maniphest Tasks: T1702

Differential Revision: https://devcentral.nasqueron.org/D2639