This reverts feb748f488 and 7cd7077467. `bootstrap_options` is meant for flag options such as `-D`. This is demonstrated in the example Vagrantfile from the original plugin: github.com/saltstack/salty-vagrant/blob/develop/example/complete/Vagrantfile Flag options must be appended to the options string before install args such as `install_type` and `install_args`.
Vagrant Core Plugins
These are plugins that ship with Vagrant. Vagrant core uses its own plugin system to power a lot of the core pieces that ship with Vagrant. Each plugin will have its own README which explains its specific role.