Fix still installing ipfilter rc.d files even when WITHOUT_IPFILTER
is specified.

When WITHOUT_IPFILTER is specified, delete-old-files fails to delete
the optional rc.d files from above. Fix this.

WITHOUT_IPFILTER fails to delete the ipfilter.5 optional file during
delete-old-files. Fix this.

Reported by: Dmitry Luhtionov <dmitryluhtionov@gmail.com>
MFC after: 1 week