selftests/bpf: Ensure sleepable program is rejected by hash map iter

Add a test to ensure sleepable program is rejected by hash map iterator.

Signed-off-by: Hou Tao <houtao1@huawei.com>
Acked-by: Yonghong Song <yhs@fb.com>
Link: https://lore.kernel.org/r/20220810080538.1845898-10-houtao@huaweicloud.com


Signed-off-by: Alexei Starovoitov <ast@kernel.org>