crypto/engine/eng_openssl.c: define TEST_ENG_OPENSSL_RC4_P_INIT conditionally

When OpenSSL is configured with 'no-stdio', TEST_ENG_OPENSSL_RC4_P_INIT
shouldn't be defined, as that test uses stdio.

Fixes #9597

Reviewed-by: Matt Caswell <matt@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/9598)

(cherry picked from commit 9f643f54236d6cf0d0d24327acd3b858883f0686)