Adding support for socket parameter in real_connect

[jkersu]

Great module!

How would you feel about adding the option to also specify the socket parameter to the real_connect call as its currently set to be null.

I've ran into an issue where I need to override the socket value but there's no way to actually pass it in. I have slightly modified the module to also include this parameters and its holding up against my testing on GCP and can make a PR if you think its worthwhile.

[elliot-sawyer]

Pull requests welcome! I see you've left some comments on the issue I raised about it (silverstripe/silverstripe-framework#9394). I haven't had an urgent need to fix it myself, but if you've gone through the trouble I'd love to have a look.