SSL_AEAD_CTX ownership is currently too confusing. Instead, rely on the lack of
renego, so the previous epoch always uses the NULL cipher. (Were we to support
DTLS renego, we could keep track of s->d1->last_aead_write_ctx like
s->d1->last_write_sequence, but it isn't worth it.)
Buffered messages also tracked an old s->session, but this is unnecessary. The
s->session NULL check in tls1_enc dates to the OpenSSL initial commit and is
redundant with the aead NULL check.
Change-Id: I9a510468d95934c65bca4979094551c7536980ae
Reviewed-on: https://boringssl-review.googlesource.com/3234
Reviewed-by: Adam Langley <agl@google.com>
afbc63fc2f