Improve testing harness to allow tests on real devices (#197)

* test_cli: provide return values to patched objects to avoid warning about non-awaited calls

* test_cli: restore alias after testing

* smartstrip: remove internal update() calls for turn_{on,off}, set_led

* Make sure power is always a float

* Fix discovery tests

* Make tests runnable on real devices

* Add a note about running tests on a real device

* test_strip: run update against the parent device

kasa/smartdevice.py

@@ -603,7 +603,7 @@ class SmartDevice:
             raise SmartDeviceException("Device has no emeter")
 
         response = EmeterStatus(await self.get_emeter_realtime())
-        return response["power"]
+        return float(response["power"])
 
     async def reboot(self, delay: int = 1) -> None:
         """Reboot the device.
@@ -658,7 +658,8 @@ class SmartDevice:
     def device_id(self) -> str:
         """Return unique ID for the device.
 
-        This is the MAC address of the device.
+        If not overridden, this is the MAC address of the device.
+        Individual sockets on strips will override this.
         """
         return self.mac