Another fix for servers that don't support byte ranges.
Another fix for servers that don't support byte ranges.

The comment in the code explains this pretty well, but
to avoid fetching different packages from different mirrors,
have Oz pick a single mirror (in the case of a redirect) up-front
and verify that it supports byte-ranges.  If it doesn't, try to
pick another mirror (up to 5 times) to try to find one that
does.  If no mirrors that support byte ranges can be found,
give up.

Signed-off-by: Chris Lalancette <60b62644009db6b194cc0445b64e9b27bb26433a@redhat.com>

nullr0ute/oz,ndonegan/oz,cernops/oz,moofrank/oz,imcleod/oz,NeilBryant/oz,moofrank/oz,NeilBryant/oz,cernops/oz,clalancette/oz,clalancette/oz,imcleod/oz,mgagne/oz,mgagne/oz,ndonegan/oz,nullr0ute/oz