test/namemap_internal_test.c: use "cookie" instead of "foo"...

test/namemap_internal_test.c: use "cookie" instead of "foo"...

... in test_namemap()

Because tests may sometimes run in random order (subject of the
environment variable OPENSSL_TEST_RAND_ORDER being defined), and we're
dealing with the global namemap, each test must use names that are
globally unique for that test.  Unfortunately, we used "foo" in two of
them, which might lead to surprising results.

Fixes #10401

Reviewed-by: Tomas Mraz <tmraz@fedoraproject.org>
(Merged from https://github.com/openssl/openssl/pull/10601)