When surrounding the version with quotes, even no version (an empty
string) will be accepted as parameter. The install.sh script treats an
empty version string the same as no when version is set. So it will
then just use the latest available version.
Before this option (`os_type`) the provisioner would use the connection
type to determine the targeted OS. When not supplying a value for
`os_type`, it will fall back to the old behaviour, so this is full BC.
Jeroen de Korte