If an instance (vm) is being destroyed a GET for all instances could fail.
This needs to be fix in rbovirt by adding a rescue in vm_interfaces to
catch where a vm is being destroyed.
def vm_interfaces vm_id
http_get("/vms/%s/nics" % vm_id, http_headers).xpath('/nics/nic').collect do |nic|
rescue # Catch case were vm_id is destroyed.