tcp: fix handling of TIME WAIT for local TCP connections

The sysctl-variable net.inet.tcp.nolocaltimewait should affect
TCP connections where the remote endpoint is on the local host and
not on the local area network.

Reported by: cc
Reviewed by: cc
MFC after: 1 week
Sponsored by: Netflix, Inc.
Differential Revision: https://reviews.freebsd.org/D50830