Write auth/token/roles/salt-node in vault bootstrap DRP script

Summary: This role is used by Salt to create tokens with policies per node.

Test Plan:

• Rewrote the policy with that command
• Ask a credential username on Dwellers, that succeeded

Reviewers: DorianWinty

Reviewed By: DorianWinty

Differential Revision: https://devcentral.nasqueron.org/D3403