Auto download the bootstrap-script at package build time.
Auto download the bootstrap-script at package build time.

Whenever the salt-cloud package is build, we now download the defined version of the salt-bootstrap.
A choice is also given to the user to provide a different bootstrap script version, one only needs to set `BOOTSTRAP_SCRIPT_VERSION` to an existing tag.

saltstack/salt,saltstack/salt,saltstack/salt,saltstack/salt,saltstack/salt