Fall back to curl and then to wget if update of metadata failed
Fall back to curl and then to wget if update of metadata failed

Our makeshift HTTP client doesn't support proxies and for installing
HTTP::UserAgent people may need a working panda. So we try using the "curl"
or "wget" commands to download the metadata file if the other options failed.

jonathanstowe/panda,stmuk/panda,timo/panda,nbrown/panda,jonathanstowe/panda,tadzik/panda,stmuk/panda,nbrown/panda,timo/panda,tadzik/panda,tadzik/panda