Remove cipher from SSL_SESSION.

Remove cipher from SSL_SESSION.

For a long time SSL_SESSION has had both a cipher ID and a pointer to
an SSL_CIPHER (and not both are guaranteed to be populated). There is also
a pointer to an SSL_CIPHER in the SSL_HANDSHAKE that denotes the cipher
being used for this connection. Some code has been using the cipher from
SSL_SESSION and some code has been using the cipher from SSL_HANDSHAKE.

Remove cipher from SSL_SESSION and use the version in SSL_HANDSHAKE
everywhere. If resuming from a session then we need to use the SSL_SESSION
cipher ID to set the SSL_HANDSHAKE cipher. And we still need to ensure that
we update the cipher ID in the SSL_SESSION whenever the SSL_HANDSHAKE
cipher changes (this only occurs in a few places).

ok tb@