selftests: bpf: test batch lookup on array of maps with holes

Iterating through array of maps may encounter non existing keys. The
batch operation should not fail on when this happens.

Signed-off-by: Yan Zhai <yan@cloudflare.com>
Acked-by: Hou Tao <houtao1@huawei.com>
Link: https://lore.kernel.org/r/9007237b9606dc2ee44465a4447fe46e13f3bea6.1739171594.git.yan@cloudflare.com


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