Don't require a local sshd for the local TCP state dtrace test

This change is similar to the one done in r286171 for
tst.ipv4localtcp.ksh. This not only reduces the requirements on the
system used for testing but results also in a graceful teardown of
the TCP connection.

Reviewed by: gnn@
Sponsored by: Netflix, Inc.
Differential Revision: https://reviews.freebsd.org/D16276