Allow dbus-daemon --nofork on Windows
On Windows, the dbus-daemon is not able to fork (daemonize). If someone
explicitly requests forking, it should fail, but if someone
explicitly requests *not* forking, there seems no harm in allowing it.
A few of the regression tests specifically require a dbus-daemon that
will not fork, so allowing this option on Windows means those tests
don't need an extra OS condition.
Bug: https://bugs.freedesktop.org/show_bug.cgi?id=68852
Reviewed-by: Ralf Habacker <ralf.habacker@freenet.de>