Sanity bot should give -1 if provisioning scripts depend on external servers or repositories

Sanity bot should give -1 if provisioning scripts depend on external servers or repositories.

• direct wget and curl commands should be avoided, "DownloadURL" should be used instead
• all "DownloadURL" commands should contain both an internally cached URL and an external one
• reachability of internal URL should be verified
• git clone should be avoided, instead tarballs (mirrored internally) should be downloaded using DownloadURL