Shall we add config for capturing the docker container id?

[jcchavezs]

Right not we capture the container ID whenever we are in a containerised environment. While this is something we want to do, I wonder if we should make it configurable or not, mostly because it is something that is not explicitly captured (e.g. https://github.com/hypertrace/goagent/pull/53/files#diff-1ff1150a465ccf63363ac0f2b5b8725a48f4156480e5dd01f439be226109642cR27)