LinuxAdmin::Disk.local doesn't work in RHEL6 in AWS

In RHEL6 on AWS, the disk devices show up like this:
/dev/xvda

In disk.rb, line 56, the Dir.glob does't allow for devices to start with 'xv':
Dir.glob('/dev/[vhs]d[a-z]').collect do |d|

Therefore local disks don't show up.

I believe this is broken for all Xen paravirt guests (xvd\* is the norm), but I have no way to confirm that.
