Fix SSL_get0_chain_certs.

SSL_get0_chain_certs calls a ctrl function with
SSL_CTRL_GET_CHAIN_CERTS. The switch failed to set a positive return
value and so the call always appeared to fail.

Change-Id: If40ca7840197a9748fd69b761fd905f44bb79835
Reviewed-on: https://boringssl-review.googlesource.com/4521
Reviewed-by: Adam Langley <agl@google.com>
diff --git a/ssl/s3_lib.c b/ssl/s3_lib.c
index 4537e2e..76441d0 100644
--- a/ssl/s3_lib.c
+++ b/ssl/s3_lib.c
@@ -708,6 +708,7 @@
 
     case SSL_CTRL_GET_CHAIN_CERTS:
       *(STACK_OF(X509) **)parg = s->cert->key->chain;
+      ret = 1;
       break;
 
     case SSL_CTRL_SELECT_CURRENT_CERT: