add CIDR format to warewulf.conf parse

Description of the Pull Request (PR):

when parsing warewulf.conf, CIDR format will cause issue.

This fixes or addresses the following GitHub issues:

• Fixes #1130

Before submitting a PR, make sure you have done the following:

• [ ] Signed off on all commits (e.g., using git commit --signoff) in agreement to the DCO
• [ ] Read the documentation for contributing to Warewulf
• [ ] Added changes to the CHANGELOG if necessary
• [ ] Updated userdocs if necessary
• [ ] Based this PR against the appropriate branch (typically main)
• [ ] Added myself as a contributor to the Contributors File