Fix signed/unsigned comparison warnings in sslapitest
Fix signed/unsigned comparison warnings in sslapitest

Fixes build failures if using enable-ktls in conjunction with --strict-warnings

Reviewed-by: Paul Dale <ddec78389666b4f7c9b4d110380c848489a3e4aa@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/16090)

openssl/openssl,openssl/openssl,openssl/openssl,openssl/openssl,openssl/openssl,openssl/openssl