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