First catched bugs with new Infra

Use alternative approach for downloading the Mongo key, avoiding https://www.mongodb.org/

Actual Ansible error:
> Failed to validate the SSL certificate for www.mongodb.org:443. Make sure your managed systems have a valid CA certificate installed. If the website serving the url uses SNI you need python >= 2.7.9 on your managed machine or you can install the `urllib3`, `pyopenssl`, `ndg-httpsclient`, and `pyasn1` python modules to perform SNI verification in python >= 2.6. You can use validate_certs=False if you do not need to confirm the servers identity but this is unsafe and not recommended. Paths checked for this platform: /etc/ssl/certs, /etc/pki/ca-trust/extracted/pem, /etc/pki/tls/certs, /usr/share/ca-certificates/cacert.org, /etc/ansible

This is needed, since `debian wheezy`, `debian jessie`, `ubuntu xenial` packages at the moment are available only in `staging` repos

kitchen-sync allows using sftp instead of scp, try to avoid random Travis build error when transferring files.