Fix Debian compatibility

APT uses "amd64" instead of "x86_64" as the architecture label. Debian doesn't come with a `nobody` group, but uses `nogroup` instead. However, since the owner is `root`, I used the `root` group as well.

Gluster's repo is a little weird in that "wheezy" is hard-coded in the URL.
This change of group might be debian specific. If it is, okay, but then put it in the os-independent params.pp file along with yaml data.