[3.9] gh-119461: Fix ThreadedVSOCKSocketStreamTest (GH-129171) (GH-129440) (#130075)

[3.9] gh-119461: Fix ThreadedVSOCKSocketStreamTest (GH-129171) (GH-129440) (#130075)

Fix ThreadedVSOCKSocketStreamTest: if get_cid() returns the host
address or the "any" address, use the local communication address
(loopback): VMADDR_CID_LOCAL.

On Linux 6.9, apparently, the /dev/vsock device is now available but
get_cid() returns VMADDR_CID_ANY (-1).

(cherry picked from commit 45db419c3104a14007ea9efbc4bff03aef8ed10c)
(cherry picked from commit e94dbe4ed83460f18bd72563c5f09f6cdc71f604)
(cherry picked from commit c750061047ee520d8299334df4b112fd983d7e48)
(cherry picked from commit cbfe3023e46b544b80ea1a38a8c900c6fb881554)

---

Restore the skipUnless removed by GH-119465.

This test can only pass on virtual machines, not actual machines.
Actual machines see:

```
    self.cli.connect((cid, VSOCKPORT))
    ~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^
OSError: [Errno 19] No such device
```

Reproduced on (Linux) Ubuntu 24.04.1 running 6.8.0-52-generic.

(cherry picked from commit 2bd9f9b0547f6ffe40cd1dd964459ce11b58144d)

Co-authored-by: Victor Stinner <vstinner@python.org>
Co-authored-by: Gregory P. Smith <greg@krypto.org>
Co-authored-by: Petr Viktorin <encukou@gmail.com>