Switch to netconf connection type

This is the recommended way from Ansible 2.5. There is no need to have specific variables for user / ssk key... The ansible defaults are used.

See https://docs.ansible.com/ansible/latest/porting_guides/porting_guide_2.5.html?highlight=netconf#network and https://docs.ansible.com/ansible/latest/plugins/connection/netconf.html

Could you please review those changes and see if you agree?

There is one thing I don't like. I couldn't make it work without using "localhost" in the playbook. We should be able to use "all", but I guess there is some interference with molecule. I need to investigate more.