Propagate pending exception from cert_client_cb

There can be a pending exception in the cert_client_cb if the server
certificate failed verification and the server requested a client
certificate. Since the handshake is going to be terminated, just
return from client_cert_cb immediately indicating no client cert will be
provided, allowing the existing exception to propagate.

Bug: 3149826
Change-Id: If95db36fc296ec9945c052a6c839e70dcd083d7b
1 file changed