Fix provider_config merging for disk config
Fix provider_config merging for disk config

mitchellh/vagrant,mitchellh/vagrant,sni/vagrant,marxarelli/vagrant,sni/vagrant,chrisroberts/vagrant,marxarelli/vagrant,marxarelli/vagrant,chrisroberts/vagrant,chrisroberts/vagrant,marxarelli/vagrant,sni/vagrant,chrisroberts/vagrant,sni/vagrant,mitchellh/vagrant,mitchellh/vagrant