Update URLs in clusterhq-release.

Use HTTPS URLs and fix the source URL.

@lukemarsden was asking how to get the source RPMs. The answer is
```shell
yum install https://storage.googleapis.com/archive.clusterhq.com/fedora/clusterhq-release$(rpm -E %dist).noarch.rpm
yumdownloader python-flocker
```
But I tried it and found that the URL was wrong.