selftests: netconsole: ignore busywait errors

selftests: netconsole: ignore busywait errors

In these netconsole tests, bash is used with errexit (set -e). It means
that if the busywait timeout, the tests finish without printing an error
message.

It is fine to ignore these errors, because the following validate_xxx
helpers will check the content of the output file, and exit with an
appropriated error message, e.g. FAIL: File was not generated.

Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
Reviewed-by: Breno Leitao <leitao@debian.org>
Link: https://patch.msgid.link/20260710-net-sft-fix-containers-v1-7-a2915c294ef5@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>