Remove unnecessary rc_post from rc.d/nsd.

Remove unnecessary rc_post from rc.d/nsd.

It was there to try and ensure that failure was reported if nsd stopped
shortly after startup (as it used to do if the address was in use, etc),
but this is no longer the case with nsd 4 which returns a failure at
startup in these cases, and having it there breaks properly printing
"(ok)" when stopping.