Provide a map with the list of servers configured through Salt

Summary:
We don't take Eglide, as it's not a Nasqueron server stricto sensu.

Ref T1691

Test Plan: Use it with https://infra.nasqueron.org/config

Reviewers: dereckson

Reviewed By: dereckson

Maniphest Tasks: T1691

Differential Revision: https://devcentral.nasqueron.org/D2554