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.

(Imported from upstream's
https://boringssl-review.googlesource.com/#/c/4521/)

Change-Id: Ia69c404c528b0cb01c7ff5e56ca8a8415265fa73
diff --git a/src/ssl/s3_lib.c b/src/ssl/s3_lib.c
index d33a4c2..e0ccedc 100644
--- a/src/ssl/s3_lib.c
+++ b/src/ssl/s3_lib.c
@@ -841,6 +841,7 @@
 
     case SSL_CTRL_GET_CHAIN_CERTS:
       *(STACK_OF(X509) **)parg = s->cert->key->chain;
+      ret = 1;
       break;
 
     case SSL_CTRL_SELECT_CURRENT_CERT: