This is a follow up to:
commit b8e3a87a ("bpf: Add crosstask check to __bpf_get_stack").

This test ensures that the task iterator only gets a single
user stack (for the current task).
Signed-off-by: Jordan Rome <linux@jordanrome.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: Stanislav Fomichev <sdf@google.com>
Link: https://lore.kernel.org/bpf/20231112023010.144675-1-linux@jordanrome.com