apps/s_server: Add missing check for BIO_new
apps/s_server: Add missing check for BIO_new

As the potential failure of the BIO_new(), it should be better to check the return value and return error if fails in order to avoid the dereference of NULL pointer.
And because 'bio_s_msg' is checked before being used everytime, which has no need to add the check.
But 'bio_s_out' is not.
And since the check 'if (bio_s_out == NULL)' is redundant, it can be removed to make the code succincter.
Also the 'sbio' and so forth should be checked like the other places in the same file.

Signed-off-by: Jiasheng Jiang <jiasheng@iscas.ac.cn>

Reviewed-by: Matt Caswell <1fa2ef4755a9226cb9a0a4840bd89b158ac71391@openssl.org>
Reviewed-by: Tomas Mraz <2bc6038c3dfca09b2da23c8b6da8ba884dc2dcc2@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/17710)

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