Fix error handling at openssl_strerror_r

When bufsize == 0, openssl_strerror_r should return 0 (if _GNU_SOURCE is defined),
to be consistent with non-_GNU_SOURCE variants, which exhibit the same behavior.
Fix a few cases, where the return value of openssl_strerror_r was ignored.

Reviewed-by: Paul Dale <paul.dale@oracle.com>
(Merged from https://github.com/openssl/openssl/pull/9163)

(cherry picked from commit e7a4682d0b347f0dfba629f4601a28801e54ad67)