Update SaltStack provision to https

This changes the SaltStack bootstrap URL to use the HTTPS link from the commercial site.  Alternatives are the HTTPS link to the raw file on GitHub, but this, whilst more transparent, might break down the line.

provisioner/salt-masterless/provisioner.go

@@ -108,7 +108,7 @@ func (p *Provisioner) Provision(ui packer.Ui, comm packer.Communicator) error {
 	ui.Say("Provisioning with Salt...")
 	if !p.config.SkipBootstrap {
 		cmd := &packer.RemoteCmd{
-			Command: fmt.Sprintf("wget -O - http://bootstrap.saltstack.org | sudo sh -s %s", p.config.BootstrapArgs),
+			Command: fmt.Sprintf("wget -O - https://bootstrap.saltstack.com | sudo sh -s %s", p.config.BootstrapArgs),
 		}
 		ui.Message(fmt.Sprintf("Installing Salt with command %s", cmd))
 		if err = cmd.StartWithUi(comm, ui); err != nil {