newsyslog - Fix an old bug in newsyslog

newsyslog - Fix an old bug in newsyslog

We kept one log file more than was requested in newsyslog.conf.
This was only the case using the non-time based filenames (.0, .1,
.2 etc.).

The change also makes newsyslog clean clean up the old extra logfile
so users don't end up with a single stale logfile which won't be
rotated out.

This change also cleans up some code a bit to avoid more copy / paste
code and removes some old copy / paste code in the process.

Obtained-from: FreeBSD (r220926)