Use curl to download from github.com

Github recently removed some sslv3 ciphers - wget seems to only
enable a subset of the ciphers available so fails now, but curl
continues to succeed.

Use --no-sessionid to work around
https://bugzilla.redhat.com/show_bug.cgi?id=1098711

Change-Id: Ia110bd2d0a222e438189c10a9c1a236bd7ea3d0e
Merge commit 'refs/changes/83/86083/2' of git://gold.eng.hq.xensource.com/git/github/openstack-dev/devstack into tmpbranch
Merge commit 'refs/changes/73/102173/2' of git://gold.eng.hq.xensource.com/git/github/openstack-dev/devstack into tmpbranch