Guard against nil server.image
Guard against nil server.image

In the case that the server was created with a CBS volume, this will be
nil.

tdooner/knife-rackspace,rackspace/knife-rackspace,decklin/knife-rackspace,philoserf/knife-rackspace,martinb3/knife-rackspace,chef/knife-rackspace,srirajan/knife-rackspace,chef/knife-rackspace