Fix for #3885: Strip colors from the log when requested.

We will use two loggers: one for files with stripColors=true and
one for everything else with stripColors=args.logNoColors.
I'm not opposed to refactoring things, but with the current shape of things this code block should logically stay in _createTransports.  Now we have 2 transports created in `_createTransports` and 1 created in `init`.