softwareupdater should default to HTTPS

[choksi81]

The current update URL in the softwareupdater uses the HTTP protocol to contact the update server for every single download. This evokes a "302 Found" status code by the server, followed by a redirect to the HTTPS version of the URL. From there, the client can download the actual file (like metainfo and whatever else is to be updated). The redirection from HTTP to HTTPS is transparently handled by urllib.

This causes two times the load for no good reason on all involved machines, and effectively doubles the delay in updating due to round-trip times for every client. We should make the softwareurl use HTTPS instead.

(Note: Ignore that the software URL points to an awkward non-NYU site. It is manually adapted for every clearinghouse setup, see wiki:Local/VersionDeployment.)