Fix error handling in x509_lu.c

Reviewed-by: Richard Levitte <levitte@openssl.org>
Reviewed-by: Tomas Mraz <tmraz@fedoraproject.org>
(Merged from https://github.com/openssl/openssl/pull/9639)

(cherry picked from commit c70e2ec33943d3bd46d3d9950f774307feda832b)