fix keycloak ipv6 issue

[zhaohuabing]

Fixes: https://github.com/envoyproxy/gateway/issues/4598 Release Notes: no

Old version:

 k -n gateway-conformance-infra logs setup-keycloak-cw75d 
Defaulted container "setup-keycloak" out of: setup-keycloak, wait-for-keycloak (init)
+ /opt/keycloak/bin/kcadm.sh create users -s username=oidcuser -s enabled=true --server http://keycloak --realm master --user admin --password admin
Logging into http://keycloak as user admin of realm master
HTTPS required [invalid_request]

New version:

k -n gateway-conformance-infra exec -it keycloak-cbcd7848f-9nk7b -- bash 
bash-5.1$ /opt/keycloak/bin/kcadm.sh create users -s username=oidcuser -s enabled=true --server http://keycloak --realm master --user admin --password admin
Logging into http://keycloak as user admin of realm master
Created new user with id '73c7d50e-890c-4311-a744-150e6a29ba1

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 65.40%. Comparing base (db68027) to head (aaf9a4d). Report is 2 commits behind head on main.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #4601 +/- ## ======================================= Coverage 65.40% 65.40% ======================================= Files 211 211 Lines 31887 31887 ======================================= Hits 20855 20855 Misses 9785 9785 Partials 1247 1247 ```

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