selftests/bpf: update test_offload to use new orphaned property

- filter orphaned programs by default
- when trying to query orphaned program, don't expect bpftool failure

Cc: netdev@vger.kernel.org
Signed-off-by: Stanislav Fomichev <sdf@google.com>
Link: https://lore.kernel.org/r/20231127182057.1081138-2-sdf@google.com
Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>