selftests/bpf: Add return value checks for failed tests

The return ranges of some bpf lsm test progs can not be deduced by
the verifier accurately. To avoid erroneous rejections, add explicit
return value checks for these progs.

Signed-off-by: Xu Kuohai <xukuohai@huawei.com>
Link: https://lore.kernel.org/r/20240719110059.797546-8-xukuohai@huaweicloud.com


Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>