Add option for static IP

[jdgoldie]

Rob,

I needed to build in a XEN Server in an environment where I have to use static IP. I added the ssh_host option and a setting for ip_getter that bypasses the VM IP discovery and uses the given value.

[rdobson]

@jdgoldie thanks for the submission (apologies for the delayed response!)

I think that if a ssh_host is specified, the concept of the ip getter is not required, so I'd prefer not to add a new 'mode', rather, only use the ip getter in the case where an IP has not been specified (i.e. static).

Can we break out that change from the additional disk one? As you've pointed out, that needs a bit of a clean up which I might be able to help with if I get some time.

Thanks.