Move to download.fedoraproject.org

download.fedoraproject.org is the mirror system, while
dl.fedoraproject.org is just one system. We have seen performance issues
with dl.fedoraproject.org and using download.fedoraproject.org was a
recommended as a solution by the folks at #fedora-admin.

Local testing on a rackspace server with dl.fedoraproject.org got about
70K/s while download.fedoraproject.org got over 1M/s

Move over to https as well.

Related-Bug: #1383928
Change-Id: I318d8844cfcfbc42c1e552e443c6b793d20f321f