OCPBUGS-86225: fix PDB AlwaysAllow test failure on IPv6-primary dualstack clusters

The nginx config in the PDB test only had `listen 8080` which binds to
IPv4 only. On dualstack clusters where IPv6 is the primary family, the
kubelet probes readiness using the pod's IPv6 address. Since nginx was
not listening on IPv6, the probe got connection refused and pods never
became Ready, causing the test to time out.

Add `listen [::]:8080` so nginx accepts connections on both IPv4 and
IPv6.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: tthvo

test/extended/testdata/poddisruptionbudgets/nginx-with-delayed-ready-deployment.yaml

@@ -68,6 +68,7 @@ data:
   default.conf: |
     server {
         listen 8080;
+        listen [::]:8080;
         server_name  localhost;
         location / {
             root   /usr/share/nginx/html;