Add attribute to show who last un/set alarm (SPC) (#9906)

* Add attribute to show who last un/set alarm.

This allows showing the name of the SPC user who last
issued an arm/disarm command and also allows for
automations to depend on this value.

* Optimize

* Update spc.py

* Update spc.py

* fix

* Fix test.

* Fix for removed is_state_attr.

homeassistant/components/binary_sensor/spc.py

@@ -67,7 +67,7 @@ class SpcBinarySensor(BinarySensorDevice):
         spc_registry.register_sensor_device(zone_id, self)
 
     @asyncio.coroutine
-    def async_update_from_spc(self, state):
+    def async_update_from_spc(self, state, extra):
         """Update the state of the device."""
         self._state = state
         yield from self.async_update_ha_state()