Don't stop execution on destroy error. (does so with vmware plugin)
Use a copy of the latest docker.service from coreos-alpha
Don't use constants for vars. Causes warnings during destroy with vmware. Also made ip addr vars dynamic, based on base_ip_addr.
Reverting the mistakenly removed hostname conf for discovery vm
Disable update-engine.service in user-data. One less provisioning command per vm.
Some refactoring to reduce the number of commands

Faster provisioning and some code reusability
Use systemd drop-in to connect docker with flannel

Thanks to Oliver Soell’s cloud-config file for inspiration!
Because `vagrant up --provider vmware_fusion` is too much to type ;-)