Refactor the virtualbox 5.1 driver implementation
Refactor the virtualbox 5.1 driver implementation

mitchellh/vagrant,chrisroberts/vagrant,chrisroberts/vagrant,taliesins/vagrant,mitchellh/vagrant,crashlytics/vagrant,mitchellh/vagrant,taliesins/vagrant,bryson/vagrant,sni/vagrant,justincampbell/vagrant,gitebra/vagrant,jtopper/vagrant,benh57/vagrant,jtopper/vagrant,justincampbell/vagrant,PatrickLang/vagrant,jtopper/vagrant,mitchellh/vagrant,gitebra/vagrant,taliesins/vagrant,bshurts/vagrant,marxarelli/vagrant,gitebra/vagrant,sni/vagrant,bdwyertech/vagrant,bryson/vagrant,bryson/vagrant,crashlytics/vagrant,bdwyertech/vagrant,bryson/vagrant,benh57/vagrant,crashlytics/vagrant,justincampbell/vagrant,justincampbell/vagrant,PatrickLang/vagrant,marxarelli/vagrant,benh57/vagrant,gitebra/vagrant,crashlytics/vagrant,marxarelli/vagrant,PatrickLang/vagrant,jtopper/vagrant,sni/vagrant,bshurts/vagrant,chrisroberts/vagrant,benh57/vagrant,mwrock/vagrant,PatrickLang/vagrant,mwrock/vagrant,chrisroberts/vagrant,bshurts/vagrant,bshurts/vagrant,sni/vagrant,marxarelli/vagrant,bdwyertech/vagrant,bdwyertech/vagrant,mwrock/vagrant,mwrock/vagrant,taliesins/vagrant