Preserve session->sess_cert on ticket renewal.

Turns out the safer/simpler method still wasn't quite right. :-)
session->sess_cert isn't serialized and deserialized, which is poor. Duplicate
it manually for now. Leave a TODO to get rid of that field altogether as it's
not especially helpful. The certificate-related fields should be in the
session. The others probably have no reason to be preserved on resumptions at
all.

Test by making bssl_shim.cc assert the peer cert chain is there or not as
expected.

BUG=501220

Change-Id: I44034167629720d6e2b7b0b938d58bcab3ab0abe
Reviewed-on: https://boringssl-review.googlesource.com/5170
Reviewed-by: Adam Langley <agl@google.com>
5 files changed