1129817 - prepend process id and thread id if line is split

By including a unique identifier, it is possible to separate logs that are generated at the same time.

 [Bugzilla-1129817](https://bugzilla.redhat.com/show_bug.cgi?id=1129817)
Yes, that seems appropriate. I moved it to module level because I was concerned that a python optimization might reuse the output of `_log_id()` across threads; but I just confirmed that making it a `@staticmethod` works as expected.