katprep_maintenance: Exclude Foreman/Uyuni host by default

[stdevel]

Is your feature request related to a problem? Please describe.
As Foreman/Uyuni hosts cannot manage themselves, it would be a good idea to exclude them for maintenance (e.g. creating snapshots, installing package upgrades) by default.
Currently this needs to be done manually using -E / --exclude.

Describe the solution you'd like
The Foreman/Uyuni host is excluded by default.

Describe alternatives you've considered

Additional context