Changes frozen repo to point to mirror.rackspace.com

The rpc-slushee.rackspace.com has numerous issues, so
we have created mirror.rackspace.com/rackspaceprivatecloud
to address those issues.  All instances of rpc-slushee
have been replaced.
Merge pull request #528 from d34dh0r53/pr-527

Changes frozen repo to point to mirror.rackspace.com