selftests/bpf: test_sockmap, print additional test options

Print values of test options like apply, cork, start, end so that
individual failed tests can be identified for manual run

Acked-by: John Fastabend <john.fastabend@gmail.com>
Signed-off-by: Prashant Bhole <bhole_prashant_q7@lab.ntt.co.jp>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>