tcp: properly initialize LRD while accepting session in syncache

[rscheff]

Summary

After the recent LRD related changes, I noted that accept()ed
sessions would not honor the per-session TF_LRD flag.

Initialize this not only in tcp_newtcpcb, but also in syncache_socket.

Test Plan

drop a data segment and the retransmission on a SACK session,
verify that another retransmission happens well before the
retransmission timeout.

MFC: 2 weeks

[rscheff]

sys/netinet/tcp_syncache.c

955–956

Alternatively, the TF_LRD flag could be inherited from the listen socket here with (TF_LRD|TF_NOPUSH|TF_NODELAY)

[tuexen]

sys/netinet/tcp_syncache.c

955–956

Inheriting is what I would prefer.

[rscheff]

• inherit LRD setting from listening socket