Merge patch series "selftests/namespaces: Fix test hangs and false failures"

Ricardo B. Marlière <rbm@suse.com> says:

This series addresses three reliability problems in the namespaces selftest
suite that cause tests to hang or report incorrect results.

The first patch fixes a hang in nsid_test where the grandchild process is
not reaped during fixture teardown, leaving it alive and holding the TAP
pipe write-end open so the test runner blocks indefinitely waiting for EOF.

The second and third patches fix two problems in listns_efault_test: a
waitpid(-1) race that can cause the iterator child to be consumed during
namespace cleanup (leading to an indefinite block on the subsequent targeted
waitpid), and a false FAIL verdict on kernels that do not implement listns()
(the EFAULT tests should SKIP in that case, consistent with every other
listns test that already handles ENOSYS correctly).

Link: https://patch.msgid.link/20260407-selftests-namespaces_fixes-v1-0-59109909d88b@suse.com
Signed-off-by: Christian Brauner <brauner@kernel.org>