Maybe the use case from what the author of the plugin expect and your workflow are different?
Perhaps he does a check on first vagrant up to ensure the machine is fit?
If thats the case, I see the enhacement need to came from the plugin.
Ugly workaround would use check vagrant-triggers and do a shutdown after the first up?
seems ugly but may work in the meantime.
Other way would be move your provisioning script to packer, and create your own box, in that way you would be in the same workflow as the plugin serverspec.
Alvaro.