Fix TLSProxy end of test detection

Fix TLSProxy end of test detection

Previously TLSProxy would detect a successful handshake once it saw the
server Finished message. This causes problems with abbreviated handshakes,
or if the client fails to process a message from the last server flight.

This change additionally sends some application data and finishes when the
client sends a CloseNotify.

Reviewed-by: Tim Hudson <tjh@openssl.org>