[cleaner] Treat IPv6 netmask as part of obfuscated string

[pmoravec]

We need to add the netmask to the string to obfuscate, i.e. to the first group of matched r.e. Otherwise, '2620:52:0:25c0::/64' like string is obfuscated to '534f:53ff:fe00:0002::/64/64'.

Closes: #4124

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[packit-as-a-service]

Congratulations! One of the builds has completed. 🍾

You can install the built RPMs by following these steps:

• sudo yum install -y dnf-plugins-core on RHEL 8
• sudo dnf install -y dnf-plugins-core on Fedora
• dnf copr enable packit/sosreport-sos-4124
• And now you can install the packages.

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