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

* [3.11] gh-119461: Fix ThreadedVSOCKSocketStreamTest (GH-129171)

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)

Co-authored-by: Victor Stinner <vstinner@python.org>
(cherry picked from commit e94dbe4ed83460f18bd72563c5f09f6cdc71f604)
(cherry picked from commit c750061047ee520d8299334df4b112fd983d7e48)
(cherry picked from commit cbfe3023e46b544b80ea1a38a8c900c6fb881554)

* gh-119461: Restore the testSocket VSOCK skipUnless removed by PR #119465 (#129561)

Restore the skipUnless removed by #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.

---------

Co-authored-by: Victor Stinner <vstinner@python.org>
Co-authored-by: Gregory P. Smith <greg@krypto.org>