tcp: properly initialize LRD while accepting session in syncache

Inherit the setting from the listener socket in syncache_socket.

MFC after: 2 weeks
Reviewed By: tuexen, transport
Sponsored by: NetApp, Inc.
Differential Revision: https://reviews.freebsd.org/D42874

(cherry picked from commit f071abd92e726fc12e9256662e1f286f364252ee)