In some corner cases the check for packets
which exceed the allowed record length was missing
when KTLS is initially enabled, when some
unprocessed packets are still pending.
Add at least some tests for KTLS, since we have
currently not very much test coverage for KTLS.
Reviewed-by: Matt Caswell <matt@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/17504)