Merge branch 'vsock-test-improve-sigpipe-test-reliability'

Stefano Garzarella says:

====================
vsock/test: improve sigpipe test reliability

Running the tests continuously I noticed that sometimes the sigpipe
test would fail due to a race between the control message of the test
and the vsock transport messages.

While I was at it I also improved the test by checking the errno we
expect.

v1: https://lore.kernel.org/20250508142005.135857-1-sgarzare@redhat.com
====================

Link: https://patch.msgid.link/20250514141927.159456-1-sgarzare@redhat.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>