Force Nonstop to use fcntl(F_GETFL) in BIO_sock_nbio

Force Nonstop to use fcntl(F_GETFL) in BIO_sock_nbio

In tracking down a hang, we found that nonstop platforms were falling
into the if #ifdef FIONBIO clause in the implementation of
BIO_sock_nbio.  While the platform defines this macro, sockets set with
this continued to operate in blocking mode.  Given that the platform
also support O_NONBLOCK, adjust the ifdef to have the nonstop platform
use that method to ensure that sockets enter blocking mode

Related-To #22588

Reviewed-by: Paul Dale <pauli@openssl.org>
Reviewed-by: Tim Hudson <tjh@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/22696)