virtualbox provider not correctly removed from vagrant in packer build script

[tmcgee]

In the packer build.sh script, the line:

 "vagrant box remove welldone_server $BUILDER || true"

will not correctly remove the box for the virtualbox provider. This is because $BUILDER was recently changed to "virtualbox-iso" from "virtualbox". virtualbox is the proper vagrant provider string. Perhaps we need a $PROVIDER to make this distinction?

Also, the vagrant docs state that the second argument to vagrant box remove is deprecated and will stop working in the next version. We need to switch to using the --provider flag.