Check return value of ssl3_output_cert_chain

Based on commit 66f96fe2d519147097c118d4bf60704c69ed0635 by Steve Henson

Reviewed-by: Tim Hudson <tjh@openssl.org>
(cherry picked from commit ce5ddefc4394a0ae6c79efaffe08cf47ac659ea0)
Checkout return value of dtls1_output_cert_chain

Reviewed-by: Tim Hudson <tjh@openssl.org>
(cherry picked from commit 9beb948c0dae6056caddf46a9aa099e18905d184)