Refactor agent.c for socket initialisation

[waterkip]

I was debugging something and say that some code got duplicated. I made a small change to move the logic into one function so it can be re-used. The goal is to create a struct/class that deals with the agent socket logic so we don't need to have path, fd, etc in multiple functions. But I haven't had the time to implement that. But this is a first iteration of that rewrite.

[GPaulovics]

Thank you @waterkip