Initial commit of a XenServer builder script

You execute this script in the Rackspace cloud, it will convert the
instance to a XenServer. A minimal precise VM will be accessible through
the public IP. The XenServer will be accessible through an internal
virtual "mgt" network.

Staging VM username:
    user
XenServer's password:
    password
XenServer's IP address:
    192.168.32.2

Flavor:
    performance1-8
Image:
    Ubuntu 13.04 (Raring Ringtail) (PVHVM beta)

Change-Id: Ibe94e56f6f3ac890e7f269042bc1db525b413efe
Add experimental Xenserver image

Limit to performance flavors on rax-iad for the moment.
hacking in the xenserver tempest test job-template