Add support to only install and not start the agent

[nandac]

Summary

Let me take this opportunity to thank the developers of this role. It works well and is easier to use.

I would like a feature where I have the option to have the infrastructure agent service come up in an inactive or stopped status when an instance is launched.

In the past, I had been using the now deprecated newrelic.newrelic-infra Ansible role, which had the option nrinfragent_service_state. By setting this option to stopped the agent would be installed without starting on launch.

Is this possible with the role?

I am thinking that I would have to manually stop it using systemd which is not ideal.

Thanks in advance.