bpf: selftest: Use bpf_sk_storage in FENTRY/FEXIT/RAW_TP

This patch tests storing the task's related info into the
bpf_sk_storage by fentry/fexit tracing at listen, accept,
and connect. It also tests the raw_tp at inet_sock_set_state.

A negative test is done by tracing the bpf_sk_storage_free()
and using bpf_sk_storage_get() at the same time. It ensures
this bpf program cannot load.

Signed-off-by: Martin KaFai Lau <kafai@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20201112211320.2587537-1-kafai@fb.com