Fix energy scan duraton (#168)

Author: Shulyaka

tests/test_application.py

@@ -709,7 +709,7 @@ async def test_energy_scan(app):
     energy = await app.energy_scan(
         channels=list(range(11, 27)), duration_exp=time_s, count=count
     )
-    assert app._api._at_command.mock_calls == [mock.call("ED", time_s)] * count
+    assert app._api._at_command.mock_calls == [mock.call("ED", bytes([time_s]))] * count
     assert {k: round(v, 3) for k, v in energy.items()} == {
         11: 254.032,
         12: 253.153,

zigpy_xbee/zigbee/application.py

@@ -196,7 +196,7 @@ async def energy_scan(
         all_results = {}
 
         for _ in range(count):
-            results = await self._api._at_command("ED", duration_exp)
+            results = await self._api._at_command("ED", bytes([duration_exp]))
             results = {
                 channel: -int(rssi) for channel, rssi in zip(range(11, 27), results)
             }