Comment 4 for bug 1881874

Ubuntu 18.04; fresh Train installation; Octavia dashboard installed according to https://github.com/openstack/octavia-dashboard

Apache's error log when trying to create a lb:

```
[Wed Jun 10 16:56:43.366034 2020] [wsgi:error] [pid 2602:tid 140704590227200] [remote 192.168.0.100:40370] ERROR openstack_dashboard.api.rest.utils error invoking apiclient
[Wed Jun 10 16:56:43.366065 2020] [wsgi:error] [pid 2602:tid 140704590227200] [remote 192.168.0.100:40370] Traceback (most recent call last):
[Wed Jun 10 16:56:43.366072 2020] [wsgi:error] [pid 2602:tid 140704590227200] [remote 192.168.0.100:40370] File "/usr/lib/python3/dist-packages/openstack_dashboard/api/rest/utils.py", line 128, in _wrapped
[Wed Jun 10 16:56:43.366077 2020] [wsgi:error] [pid 2602:tid 140704590227200] [remote 192.168.0.100:40370] data = function(self, request, *args, **kw)
[Wed Jun 10 16:56:43.366082 2020] [wsgi:error] [pid 2602:tid 140704590227200] [remote 192.168.0.100:40370] File "/usr/local/lib/python3.6/dist-packages/octavia_dashboard/api/rest/lbaasv2.py", line 1410, in get
[Wed Jun 10 16:56:43.366087 2020] [wsgi:error] [pid 2602:tid 140704590227200] [remote 192.168.0.100:40370] conn.load_balancer.availability_zones()
[Wed Jun 10 16:56:43.366093 2020] [wsgi:error] [pid 2602:tid 140704590227200] [remote 192.168.0.100:40370] AttributeError: 'Proxy' object has no attribute 'availability_zones'
[Wed Jun 10 16:56:43.366101 2020] [wsgi:error] [pid 2602:tid 140704590227200] [remote 192.168.0.100:40370]
[Wed Jun 10 16:56:43.366500 2020] [wsgi:error] [pid 2602:tid 140704590227200] [remote 192.168.0.100:40370] ERROR django.request Internal Server Error: /horizon/api/lbaas/availabilityzones/
```

Maybe some configuration steps are missing and someone has some ideas. Thank You