selftests/bpf: Add txmsg_pass to pull/push/pop in test_sockmap

selftests/bpf: Add txmsg_pass to pull/push/pop in test_sockmap

Add txmsg_pass to test_txmsg_pull/push/pop. If txmsg_pass is missing,
tx_prog will be NULL, and no program will be attached to the sockmap.
As a result, pull/push/pop are never invoked.

Fixes: 328aa08a081b ("bpf: Selftests, break down test_sockmap into subtests")
Signed-off-by: Zijian Zhang <zijianzhang@bytedance.com>
Reviewed-by: John Fastabend <john.fastabend@gmail.com>
Link: https://lore.kernel.org/r/20241106222520.527076-2-zijianzhang@bytedance.com
Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>