Try to get a mirror list for network installs

[Ralf Ertzinger <fedora camperquake de>]

Hi.

When doing a network install (HTTP/FTP), could anaconda be persuaded to
try and get a list of mirrors from somewhere (using a similar approach
as the current yum mirrorlist, perhaps)? If this fails, or if the user
wants to enter a private mirror, that's fine, and the mirror can be entered
manually, but I think we ought to offer the user a list of mirrors to
install from, if possible.