fix container for ipv6

[sepauli]

Description

the tink-stack pod crashes on an ipv6 only cluster because the container can not handle IPv6 addresses

:~# kubectl logs -n tink-system tink-stack-6bbc556dd-znd6j
Defaulted container "tink-stack" out of: tink-stack, dhcp-relay
++ awk '/nameserver/ {print $2}' /etc/resolv.conf
+ POD_NAMESERVER=fd05:0000:0000::a
+ envsubst '$POD_NAMESERVER'
+ exec nginx -g 'daemon off;'
2024/06/03 16:23:37 [emerg] 3210953#3210953: invalid port in resolver "fd05:0000:0000::a" in /etc/nginx/nginx.conf:13
nginx: [emerg] invalid port in resolver "fd05:0000:0000::a" in /etc/nginx/nginx.conf:13

Why is this needed

We use an IPv6 only RKE2 Cluster and we need to start this container correctly.

Fixes: #99

How Has This Been Tested?

I tested the fix in our RKE2 IPv6 only cluster and it works. But i don't have an IPv4 environment for testing