Only save node if we're not running chef solo

Calling node.save in chef solo causes an error (complains that it can't find a client.pem file).

I've tweaked the cookbook so it only saves the node if we're not running chef solo (based on [advice here](http://stackoverflow.com/questions/19927760/chef-how-do-you-replace-node-set-node-save-in-chef-solo)).

Can someone review and let me know if this is sensible? I've tested my local branch from within the odi-quirkafleeg-backend cookbook and it resolves my error.