do_body: fix heap-use-after-free.

The memory pointed to by the 'push' is freed by the
X509_NAME_ENTRY_free() in do_body(). The second time
it is referenced to (indirectly) in certify_cert:X509_REQ_free().
Reviewed-by: NRich Salz <rsalz@openssl.org>
Reviewed-by: NMatt Caswell <matt@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/4698)

apps/ca.c

@@ -1556,7 +1556,6 @@ static int do_body(X509 **xret, EVP_PKEY *pkey, X509 *x509,
 
             if (push != NULL) {
                 if (!X509_NAME_add_entry(subject, push, -1, 0)) {
-                    X509_NAME_ENTRY_free(push);
                     BIO_printf(bio_err, "Memory allocation failure\n");
                     goto end;
                 }