Use Vagrant::Action::Builtin::Provision on Linux guests

This makes sure all required hooks, such as rsync and omnibus,
get run on provisioning. Along with chef.synced_folder_type = 'rsync'
and vagrant-omnibus makes chef-solo provisioner just work
on Linux guests.
Make sure to sync folders on provisioning
Use action_provision in action_prepare_boot
Fix autoload for WinProvision
Merge pull request #17 from dividedmind/builtin-provisioner

Use Vagrant::Action::Builtin::Provision on Linux guests