Comment 4 for bug 1072670

The extra interface down/up is that wifi ether address is to be restored to initialized address during sleep, see below
call path in network-manager:

real_hw_take_down/real_hw_take_up
 <-_set_hw_addr (self, priv->initial_hw_addr, "reset");
  <-real_deactivate() /*wifi*/
   <-nm_device_deactivate
    <-nm_device_take_down
     <-nm_device_state_changed
      <-nm_device_set_managed
       <-do_sleep_wake
        <-_internal_sleep
         <-_internal_sleep
          <-upower_sleeping_cb

So considered that the open/close cycle of wifi interface may take long time, maybe nm should be optimized
for the situation(don't do it if ether address isn't changed) or just remove the resetting address for n7.