nictagadm: don't call is_valid_mac when etherstub is true (#11589)
* nictagadm: don't call is_valid_mac when etherstub is true
* Add changelog fragment
* update changelog fragment
* Shorten changelog fragement
* Update changelogs/fragments/nictagadm-etherstub-nonetype-bugfix.yml
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(cherry picked from commit d8bb637cba)
Co-authored-by: Adam D <44533090+emptyDir@users.noreply.github.com>
Co-authored-by: Felix Fontein <felix@fontein.de>