Remove an extraneous call to soisconnected() in syncache_socket(),

introduced with r261242.  The useful and expected soisconnected()
call is done in tcp_do_segment().

Has been found as part of unrelated PR:212920 investigation.

Improve slightly (~2%) the maximum number of TCP accept per second.

Tested by:		kevin.bowling_kev009.com, jch
Approved by:		gnn, hiren
MFC after:		1 week
Sponsored by:		Verisign, Inc
Differential Revision:	https://reviews.freebsd.org/D8072

sys/netinet/tcp_syncache.c

@@ -918,10 +918,6 @@ syncache_socket(struct syncache *sc, struct socket *lso, struct mbuf *m)
 	tp->t_keepcnt = sototcpcb(lso)->t_keepcnt;
 	tcp_timer_activate(tp, TT_KEEP, TP_KEEPINIT(tp));
 
-	if ((so->so_options & SO_ACCEPTFILTER) == 0) {
-		soisconnected(so);
-	}
-
 	TCPSTAT_INC(tcps_accepts);
 	return (so);