Deduplicate code between install.yaml and update_config.yaml

Well done! Now we have a simpler and more straightforward Ansible role for managing the types of Oasis-nodes deployed by node operators.

I noticed there is a bit of code overlap between `roles/oasis_node/tasks/install.yaml` and `roles/oasis_node/tasks/update_config.yaml`. To avoid potential inconsistencies in the future, consider deduplicating it.