selftests: bpf: Fix detach from sockmap tests

Fix sockmap tests which rely on old bpf_prog_dispatch behaviour.
In the first case, the tests check that detaching without giving
a program succeeds. Since these are not the desired semantics,
invert the condition. In the second case, the clean up code doesn't
supply the necessary program fds.

Fixes: bb0de313 ("bpf: sockmap: Require attach_bpf_fd when detaching a program")
Reported-by: Martin KaFai Lau <kafai@fb.com>
Signed-off-by: Lorenz Bauer <lmb@cloudflare.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Reviewed-by: Jakub Sitnicki <jakub@cloudflare.com>
Link: https://lore.kernel.org/bpf/20200709115151.75829-1-lmb@cloudflare.com