Set ZHA device availability on new join (#21066)

* set availability on device join

* fix new join test

homeassistant/components/zha/core/gateway.py

@@ -164,6 +164,9 @@ class ZHAGateway:
         device_entity = _create_device_entity(zha_device)
         await self._component.async_add_entities([device_entity])
 
+        if is_new_join:
+            zha_device.update_available(True)
+
     async def _async_process_endpoint(
             self, endpoint_id, endpoint, discovery_infos, device, zha_device,
             is_new_join):

tests/components/zha/common.py

@@ -1,7 +1,6 @@
 """Common test objects."""
 import time
 from unittest.mock import patch, Mock
-from homeassistant.const import STATE_UNAVAILABLE
 from homeassistant.components.zha.core.helpers import convert_ieee
 from homeassistant.components.zha.core.const import (
     DATA_ZHA, DATA_ZHA_CONFIG, DATA_ZHA_DISPATCHERS, DATA_ZHA_BRIDGE_ID
@@ -191,4 +190,4 @@ async def async_test_device_join(
             cluster = zigpy_device.endpoints.get(1).in_clusters[cluster_id]
             entity_id = make_entity_id(
                 domain, zigpy_device, cluster, use_suffix=device_type is None)
-            assert hass.states.get(entity_id).state == STATE_UNAVAILABLE
+            assert hass.states.get(entity_id) is not None