Merge branch 'selftests-drv-net-improve-the-queue-test-for-xsk'

Jakub Kicinski says:

====================
selftests: drv-net: improve the queue test for XSK

We see some flakes in the the XSK test:

   Exception| Traceback (most recent call last):
   Exception|   File "/home/virtme/testing-18/tools/testing/selftests/net/lib/py/ksft.py", line 218, in ksft_run
   Exception|     case(*args)
   Exception|   File "/home/virtme/testing-18/tools/testing/selftests/drivers/net/./queues.py", line 53, in check_xdp
   Exception|     ksft_eq(q['xsk'], {})
   Exception| KeyError: 'xsk'

I think it's because the method of running the helper in the background
is racy. Add more solid infra for waiting for a background helper to be
initialized.

v1: https://lore.kernel.org/20250218195048.74692-1-kuba@kernel.org
====================

Link: https://patch.msgid.link/20250219234956.520599-1-kuba@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>