bpf, tests: Fix typos in test case descriptions

This patch corrects the test description in a number of cases where
the description differed from what was actually tested and expected.

Signed-off-by: Johan Almbladh <johan.almbladh@anyfinetworks.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Yonghong Song <yhs@fb.com>
Link: https://lore.kernel.org/bpf/20210809091829.810076-4-johan.almbladh@anyfinetworks.com