IPv6 address not regarded as a valid CN

[sjoerdsimons]

When using k3s on an dual-stacked system i'm seeing message like:

Jun 10 19:45:50 .... k3s[24961]: time="2021-06-10T19:45:50.638896992Z" level=error msg="dropping invalid CN: 2a00:0018::9b00:c0f9:80e:47:42"
Jun 10 20:09:06. .. k3s[5482]: time="2021-06-10T20:09:06.985352461Z" level=error msg="dropping invalid CN: ::1"

This is caused by the dynamic listener CN check not regarding raw ipv6 address as valid CN names