providers/virtualbox: cache VirtualBox version [GH-6468]
providers/virtualbox: cache VirtualBox version [GH-6468]

vamegh/vagrant,vamegh/vagrant,marxarelli/vagrant,bshurts/vagrant,bryson/vagrant,chrisroberts/vagrant,carlosefr/vagrant,vamegh/vagrant,bdwyertech/vagrant,gitebra/vagrant,Chhed13/vagrant,lukebakken/vagrant,carlosefr/vagrant,kamazee/vagrant,PatrickLang/vagrant,gitebra/vagrant,bdwyertech/vagrant,kamigerami/vagrant,PatOShea/vagrant,benh57/vagrant,invernizzi-at-google/vagrant,mkuzmin/vagrant,benizi/vagrant,signed8bit/vagrant,aaam/vagrant,taliesins/vagrant,sni/vagrant,justincampbell/vagrant,Chhed13/vagrant,jtopper/vagrant,signed8bit/vagrant,sni/vagrant,justincampbell/vagrant,krig/vagrant,mkuzmin/vagrant,sax/vagrant,krig/vagrant,petems/vagrant,bryson/vagrant,tomfanning/vagrant,vamegh/vagrant,krig/vagrant,bdwyertech/vagrant,justincampbell/vagrant,mwrock/vagrant,Chhed13/vagrant,sax/vagrant,johntron/vagrant,TheBigBear/vagrant,signed8bit/vagrant,chrisroberts/vagrant,benh57/vagrant,benizi/vagrant,mitchellh/vagrant,Endika/vagrant,kamazee/vagrant,sni/vagrant,sax/vagrant,aneeshusa/vagrant,petems/vagrant,aaam/vagrant,mwrock/vagrant,PatOShea/vagrant,carlosefr/vagrant,lukebakken/vagrant,marxarelli/vagrant,benizi/vagrant,tomfanning/vagrant,johntron/vagrant,bdwyertech/vagrant,bryson/vagrant,chrisroberts/vagrant,PatrickLang/vagrant,jtopper/vagrant,lonniev/vagrant,sni/vagrant,mkuzmin/vagrant,kamigerami/vagrant,PatrickLang/vagrant,invernizzi-at-google/vagrant,aneeshusa/vagrant,TheBigBear/vagrant,lonniev/vagrant,aaam/vagrant,mkuzmin/vagrant,TheBigBear/vagrant,lukebakken/vagrant,crashlytics/vagrant,crashlytics/vagrant,petems/vagrant,taliesins/vagrant,johntron/vagrant,kamazee/vagrant,PatOShea/vagrant,carlosefr/vagrant,kamigerami/vagrant,bshurts/vagrant,bryson/vagrant,tomfanning/vagrant,justincampbell/vagrant,Endika/vagrant,marxarelli/vagrant,gitebra/vagrant,tomfanning/vagrant,jtopper/vagrant,invernizzi-at-google/vagrant,TheBigBear/vagrant,krig/vagrant,marxarelli/vagrant,Chhed13/vagrant,kamazee/vagrant,bshurts/vagrant,crashlytics/vagrant,crashlytics/vagrant,benh57/vagrant,signed8bit/vagrant,johntron/vagrant,PatOShea/vagrant,PatrickLang/vagrant,mitchellh/vagrant,bshurts/vagrant,kamigerami/vagrant,gitebra/vagrant,Endika/vagrant,aaam/vagrant,aneeshusa/vagrant,benizi/vagrant,mwrock/vagrant,jtopper/vagrant,petems/vagrant,lukebakken/vagrant,mwrock/vagrant,mitchellh/vagrant,lonniev/vagrant,chrisroberts/vagrant,lonniev/vagrant,aneeshusa/vagrant,benh57/vagrant,taliesins/vagrant,invernizzi-at-google/vagrant,mitchellh/vagrant,Endika/vagrant,sax/vagrant,taliesins/vagrant