ktls: Fix assertion for TLS 1.0 CBC when using non-zero starting seqno.

The starting sequence number used to verify that TLS 1.0 CBC records
are encrypted in-order in the OCF layer was always set to 0 and not to
the initial sequence number from the struct tls_enable.

In practice, OpenSSL always starts TLS transmit offload with a
sequence number of zero, so this only matters for tests that use a
random starting sequence number.

Reviewed by:	markj
Sponsored by:	Netflix
Differential Revision:	https://reviews.freebsd.org/D32676

sys/opencrypto/ktls_ocf.c

@@ -761,6 +761,9 @@ ktls_ocf_try(struct socket *so, struct ktls_session *tls, int direction)
 		if (tls->params.tls_vminor == TLS_MINOR_VER_ZERO) {
 			os->implicit_iv = true;
 			memcpy(os->iv, tls->params.iv, AES_BLOCK_LEN);
+#ifdef INVARIANTS
+			os->next_seqno = tls->next_seqno;
+#endif
 		}
 	}