fix(is_port_used): make it more robust

[soyacz]

Reverted previous fix for wait_db_down - it was working for checking db down properly, but still is_port_used was not working right for docker backend.

So used this new working approach in is_port_used instead.

fixes: #8031

Testing

• - kill scylla nemesis
• - artifact test with public ipv6
• - docker artifact test

PR pre-checks (self review)

• I added the relevant backport labels
• I didn't leave commented-out/debugging code

Reminders

• Add New configuration option and document them (in sdcm/sct_config.py)
• Add unit tests to cover my changes (under unit-test/ folder)
• Update the Readme/doc folder relevant to this change (if needed)

[fruch]

Still has the concern of generating warning in scylla log

[soyacz]

Still has the concern of generating warning in scylla log

I didn't notice warnings related to this. In ScyllaKillMonkey warnings relate to lost connections between nodes.
I also tried running is_port_used in a loop and no effect on db whatsoever.

[soyacz]

in docker artifact test, we can now see that node startup takes ~8.5s while without this fix was ~4s (and was premature - as cql port was not up yet). extract from log (see, it waits properly with Waiting for DB services to be up: attempt 1 ended with: False message):

< t:2024-07-18 06:17:06,600 f:base.py         l:143  c:RemoteLibSSH2CmdRunner p:DEBUG > <172.17.0.2>: Command "sudo sh -c "supervisorctl start scylla || supervisorctl start scylla-server"" finished with status 0
< t:2024-07-18 06:17:06,601 f:wait.py         l:52   c:sdcm.wait            p:DEBUG > wait_for: Retrying artifacts-docker-jenkins-db-node-a9b6d5ac-0: Waiting for DB services to be up: attempt 1 ended with: False
< t:2024-07-18 06:17:11,604 f:remote_base.py  l:521  c:RemoteLibSSH2CmdRunner p:DEBUG > <172.17.0.2>: Running command "sudo sh -c "supervisorctl start scylla-housekeeping || supervisorctl start scylla-housekeeping-server""...
< t:2024-07-18 06:17:12,841 f:base.py         l:231  c:RemoteLibSSH2CmdRunner p:DEBUG > <172.17.0.2>: scylla-housekeeping: started
< t:2024-07-18 06:17:13,342 f:base.py         l:143  c:RemoteLibSSH2CmdRunner p:DEBUG > <172.17.0.2>: Command "sudo sh -c "supervisorctl start scylla-housekeeping || supervisorctl start scylla-housekeeping-server"" finished with status 0
< t:2024-07-18 06:17:13,342 f:decorators.py   l:121  c:sdcm.utils.decorators p:DEBUG > END: start_scylla <DockerNode> (ran 8.532388s)

[fruch]

LGTM

[vponomaryov]

LGTM