Clean up suspicious coordinate system use in unit_put()

Clean up suspicious coordinate system use in unit_put()

It showed unit coordinates in unit's coordinate system instead of the
actor's.  Fortunately, they're the same, since it is reachable only
for non-zero actor, only shp_nav_one_sector(), lnd_mar_one_sector()
and sail_nav_fleet() pass that, and even deities can't navigate
foreign ships or march foreign land units.