Fix a memory leak in ssl_create_cipher_list

Reviewed-by: Paul Dale <pauli@openssl.org>
Reviewed-by: Matt Caswell <matt@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/16954)

ssl/ssl_ciph.c

@@ -1643,6 +1643,7 @@ STACK_OF(SSL_CIPHER) *ssl_create_cipher_list(SSL_CTX *ctx,
         }
 
         if (!sk_SSL_CIPHER_push(cipherstack, sslc)) {
+            OPENSSL_free(co_list);
             sk_SSL_CIPHER_free(cipherstack);
             return NULL;
         }