Test CBC mode padding.

This is a regression test for
https://github.com/openssl/openssl/pull/1431

. It tests a
maximally-padded record with each possible invalid offset.

This required fixing a bug in Message.pm where the client sending a
fatal alert followed by close_notify was still treated as success.

Reviewed-by: Rich Salz <rsalz@openssl.org>
Reviewed-by: Matt Caswell <matt@openssl.org>