using --reduce-factor disables --except

[Ian! D. Allen]

This is a bug in both version `1.0.4` and version `1.0.5_master`.
See https://github.com/firehol/iprange/issues/31

First, set up two test files:

~~~~~
    $ cat <<EOF >in
    1.2.3.4
    1.2.3.5
    1.2.3.6
    9.9.9.6
    9.9.9.7
    9.9.9.8
    9.9.9.9
    EOF

    $ cat <<EOF >except
    1.2.3.4
    1.2.3.5
    1.2.3.6
    EOF
~~~~~

Without using `--reduce-factor` I get the expected output:

~~~~~
    $ iprange in --except except >out
    $ iprange in --diff out
    1.2.3.4/31
    1.2.3.6
~~~~~

Using any value of `--reduce-factor` causes the `--except` to be ignored:

~~~~~
    $ iprange in --except except --reduce-factor 0 >out
    $ iprange in --diff out
    $ iprange in --except except --reduce-factor 10 >out
    $ iprange in --diff out
    $ iprange in --except except --reduce-factor 90 >out
    $ iprange in --diff out
    $ diff in out
    $
~~~~~

ProblemType: Bug
DistroRelease: Ubuntu 20.04
Package: iprange 1.0.4+ds-2
ProcVersionSignature: Ubuntu 5.13.0-39.44~20.04.1-generic 5.13.19
Uname: Linux 5.13.0-39-generic x86_64
ApportVersion: 2.20.11-0ubuntu27.21
Architecture: amd64
CasperMD5CheckResult: skip
Date: Tue Apr 5 00:37:04 2022
EcryptfsInUse: Yes
InstallationDate: Installed on 2020-10-07 (544 days ago)
InstallationMedia: Lubuntu 20.04.1 LTS "Focal Fossa" - Release amd64 (20200731)
SourcePackage: iprange
UpgradeStatus: No upgrade log present (probably fresh install)