Merge r262763, r262767, r262771, r262806 from head:
  - Remove rt_metrics_lite and simply put its members into rtentry.
  - Use counter(9) for rt_pksent (former rt_rmx.rmx_pksent). This
    removes another cache trashing ++ from packet forwarding path.
  - Create zini/fini methods for the rtentry UMA zone. Via initialize
    mutex and counter in them.
  - Fix reporting of rmx_pksent to routing socket.
  - Fix netstat(1) to report "Use" both in kvm(3) and sysctl(3) mode.