use new check_url_available promise from slapos.toolbox 0.123

This follows the changes to the check_url_available promise in nexedi/slapos.toolbox proposed in https://lab.nexedi.com/nexedi/slapos.toolbox/merge_requests/98. Briefly:

• rename http_code to http-code
• change check-secure = 1 to http-code = 401
• increment version of slapos.toolbox egg.

We also use the new password check feature in the monitoring stack.