Fix return value checking for BIO_sock_init

BIO_sock_init returns '-1' on error, not '0', so it's needed to check
explicitly istead of using '!'.

Reviewed-by: Tim Hudson <tjh@openssl.org>
Reviewed-by: Bernd Edlinger <bernd.edlinger@hotmail.de>
(Merged from https://github.com/openssl/openssl/pull/3766)