* Update list of directory servers from current Tor source
* Since consensus is agreed on by all directories, stop after retrieving the first one.
* Use numeric port number, not string. http.lua to be updated later to allow strings, too.
* Do not use http.lua's cache for this big document, since we're caching it ourselves.
* Permit sizes up to 3 MiB, since consensus is larger than default 2 MiB limit.
