Improvements to chef-client firstboot script
 - Chef for network connectivity before going ahead with the chef-client download. This is to resolve what I've found to be a common cause of the firstboot script failure.
 - Make the use of validation_client_name optional.
 - If a server role is set, use it.
 - Use the proper service start convention, instead of the init.d script directly.
 - Some remarks for posterity.
Enhance preseed by using site.config entries more
1. Move the defaults from views.py into the default site.config data
2. Add more site.config entries for other preseed values
3. Remove some duplicated preseed file lines
Add OVS and utility network interface flags
Improvements to the debian post install script
Make the chef-client script install OVS and setup utility networks as required
Host model changes for OVS and utility networks