Description of problem:
On RHOS-16.2-RHEL-8-20201014.n.3

(undercloud) [stack@undercloud-0 ~]$ openstack overcloud node import --instance-boot-option=local /home/stack/instackenv.json
Could not establish a connection to the Zaqar websocket. The command was sent but the answer could not be read.
Exception occured while running the command
Traceback (most recent call last):
  File "/usr/lib/python3.6/site-packages/tripleoclient/command.py", line 32, in run 
    super(Command, self).run(parsed_args)
  File "/usr/lib/python3.6/site-packages/osc_lib/command/command.py", line 41, in run 
    return super(Command, self).run(parsed_args)
  File "/usr/lib/python3.6/site-packages/cliff/command.py", line 185, in run 
    return_code = self.take_action(parsed_args) or 0
  File "/usr/lib/python3.6/site-packages/tripleoclient/v1/overcloud_node.py", line 412, in take_action
    instance_boot_option=parsed_args.instance_boot_option
  File "/usr/lib/python3.6/site-packages/tripleoclient/workflows/baremetal.py", line 62, in register_or_update
    with tripleoclients.messaging_websocket() as ws: 
  File "/usr/lib/python3.6/site-packages/tripleoclient/plugin.py", line 223, in messaging_websocket
    cacert=self._instance.cacert)
  File "/usr/lib/python3.6/site-packages/tripleoclient/plugin.py", line 91, in __init__
    self._ws = websocket.create_connection(endpoint)
  File "/usr/lib/python3.6/site-packages/websocket/_core.py", line 511, in create_connection
    websock.connect(url, **options)
  File "/usr/lib/python3.6/site-packages/websocket/_core.py", line 220, in connect
    options.pop('socket', None))
  File "/usr/lib/python3.6/site-packages/websocket/_http.py", line 120, in connect
    sock = _open_socket(addrinfo_list, options.sockopt, options.timeout)
  File "/usr/lib/python3.6/site-packages/websocket/_http.py", line 190, in _open_socket
    raise err 
  File "/usr/lib/python3.6/site-packages/websocket/_http.py", line 170, in _open_socket
    sock.connect(address)
ConnectionRefusedError: [Errno 111] Connection refused
[Errno 111] Connection refused
sys:1: ResourceWarning: unclosed <socket.socket fd=7, family=AddressFamily.AF_INET, type=SocketKind.SOCK_STREAM, proto=6, laddr=('0.0.0.0', 43246)>
sys:1: ResourceWarning: unclosed <ssl.SSLSocket fd=6, family=AddressFamily.AF_INET, type=SocketKind.SOCK_STREAM, proto=6, laddr=('192.168.24.2', 40540), raddr=('192.168.24.2', 13000)>
 
 
The exact address it wants to connect to is: '192.168.24.2', 3000). Indeed I see no processes listening on port 3000
 
On an older working osp16.1 I see the following:
 [root@undercloud-0 stdouts]# ss -ntaulpen |grep :3000
tcp   LISTEN 0      128                       192.168.24.2:3000         0.0.0.0:* users:(("haproxy",pid=49434,fd=32)) ino:272791 sk:1d <-> 
 
So haproxy must be misconfigured here and in fact we're missing the following stanza on 16.2:
listen zaqar_ws
  bind 192.168.24.2:3000 ssl crt /etc/pki/tls/private/overcloud_endpoint.pem
  bind 192.168.24.3:9000
  mode http
  http-request set-header Host %[dst]:9000
  option forwardfor
  redirect scheme https code 301 if { hdr(host) -i 192.168.24.2 } !{ ssl_fc }
  rsprep ^Location:\ http://(.*) Location:\ https://\1
  timeout connect 5s
  timeout client 25s 
  timeout server 25s 
  timeout tunnel 14400s
  server undercloud-0 192.168.24.1:9000 check fall 5 inter 2000 rise 2