[xfer] Implement xfer_vreopen() to properly handle redirections

When handling a redirection event, we need to close the existing
connection before opening the new connection.

src/net/tls.c

@@ -1625,7 +1625,7 @@ static int tls_cipherstream_deliver_raw ( struct xfer_interface *xfer,
 /** TLS ciphertext stream operations */
 static struct xfer_interface_operations tls_cipherstream_operations = {
 	.close		= tls_cipherstream_close,
-	.vredirect	= xfer_vopen,
+	.vredirect	= xfer_vreopen,
 	.window		= filter_window,
 	.alloc_iob	= default_xfer_alloc_iob,
 	.deliver_iob	= xfer_deliver_as_raw,