Ensure (n>1)-th page of references does not re-request first page from lsif-server
Created by: efritz
We request the first page of results (a POST without a cursor value) whenever we don't have a next URL from a previous request.
We ensure that we either have an empty cursor map (first requests for all uploads), or a non-empty cursor map (making only requests for which we have a previous cursor). This stops us from requesting without a cursor for an upload we've already queried.