[test_cacl_application.py] Docker inspect bridge IPV6 enable?

[tim-rj]

Description

Hi, I am running the test case cacl/test_cacl_application.py.
Due to the PR: #3070, there are some updates:

docker_network['bridge'] = {'IPv4Address' : ipam_info['Config'][0]['Gateway'],
'IPv6Address' : ipam_info['Config'][1]['Gateway'] }

However, an error happend when obtaining IPV6 address from docker inspect bridge:

root@str-msn2700-01:/etc/docker# docker inspect bridge
[
{
"Name": "bridge",
"Id": "288bed8f6c777f09cc1ca972e4fc3099e4a2b3b8469f475cf2216a1f2d947381",
"Created": "2021-04-16T05:13:04.115499907Z",
"Scope": "local",
"Driver": "bridge",
"EnableIPv6": false,
"IPAM": {
"Driver": "default",
"Options": null,
"Config": [
{
"Subnet": "240.127.1.1/24",
"Gateway": "240.127.1.1"
}
]
},
"Internal": false,
"Attachable": false,
"Ingress": false,
"ConfigFrom": {
"Network": ""
},
"ConfigOnly": false,
"Containers": {},
"Options": {
"com.docker.network.bridge.default_bridge": "true",
"com.docker.network.bridge.enable_icc": "true",
"com.docker.network.bridge.enable_ip_masquerade": "false",
"com.docker.network.bridge.host_binding_ipv4": "0.0.0.0",
"com.docker.network.bridge.name": "docker0",
"com.docker.network.driver.mtu": "1500"
},
"Labels": {}
}
]

"EnableIPv6": false, --------->Here is false. It seems that my "docker inspect bridge" only has one gateway for ipv4. I am wondering how to make it true to apply the updated cacl/test_cacl_application.py?

Steps to reproduce the issue:

1. Deploy t0
2. Run cacl/test_cacl_application.py

Describe the results you received:
Error

Describe the results you expected:
Pass as before...

Additional information you deem important:

**Output of `show version`:**

```

201911
```

**Attach debug file `sudo generate_dump`:**

N/A