Clear all data from DB table when the daemon stops (#228)

Description
Clear all data from DB table when the daemon stops

Motivation and Context
Clean up when the daemon stops

How Has This Been Tested?
Check Thermal and physical info data if they are cleared after stopping the thermalctld.

sonic-thermalctld/scripts/thermalctld

@@ -206,13 +206,19 @@ class FanUpdater(logger.Logger):
         self.drawer_table = swsscommon.Table(state_db, FanUpdater.FAN_DRAWER_INFO_TABLE_NAME)
         self.phy_entity_table = swsscommon.Table(state_db, PHYSICAL_ENTITY_INFO_TABLE)
 
-    def deinit(self):
-        """
-        Deinitializer of FanUpdater
-        :return:
-        """
-        for name in self.fan_status_dict.keys():
-            self.table._del(name)
+    def __del__(self):
+        if self.table:
+            table_keys = self.table.getKeys()
+            for tk in table_keys:
+                self.table._del(tk)
+        if self.drawer_table:
+            drawer_keys = self.drawer_table.getKeys()
+            for dtk in drawer_keys:
+                self.drawer_table._del(dtk)
+        if self.phy_entity_table:
+            phy_entity_keys = self.phy_entity_table.getKeys()
+            for pek in phy_entity_keys:
+                self.phy_entity_table._del(pek)
 
     def _log_on_status_changed(self, normal_status, normal_log, abnormal_log):
         """
@@ -550,6 +556,16 @@ class TemperatureUpdater(logger.Logger):
                 except Exception as e:
                     self.chassis_table = None
 
+    def __del__(self):
+        if self.table:
+            table_keys = self.table.getKeys()
+            for tk in table_keys:
+                self.table._del(tk)
+        if self.phy_entity_table:
+            phy_entity_keys = self.phy_entity_table.getKeys()
+            for pek in phy_entity_keys:
+                self.phy_entity_table._del(pek)
+
     def deinit(self):
         """
         Deinitializer of TemperatureUpdater
@@ -778,7 +794,6 @@ class ThermalMonitor(ProcessTaskBase):
         while not self.task_stopping_event.wait(self.wait_time):
             self.main()
 
-        self.fan_updater.deinit()
         self.temperature_updater.deinit()
 
         self.logger.log_info("Stop thermal monitoring loop")

sonic-thermalctld/tests/test_thermalctld.py

@@ -154,16 +154,6 @@ class TestFanUpdater(object):
     """
     Test cases to cover functionality in FanUpdater class
     """
-    def test_deinit(self):
-        fan_updater = thermalctld.FanUpdater(MockChassis(), multiprocessing.Event())
-        fan_updater.fan_status_dict = {'key1': 'value1', 'key2': 'value2'}
-        fan_updater.table._del = mock.MagicMock()
-
-        fan_updater.deinit()
-        assert fan_updater.table._del.call_count == 2
-        expected_calls = [mock.call('key1'), mock.call('key2')]
-        fan_updater.table._del.assert_has_calls(expected_calls, any_order=True)
-
     @mock.patch('thermalctld.try_get', mock.MagicMock(return_value=thermalctld.NOT_AVAILABLE))
     @mock.patch('thermalctld.update_entity_info', mock.MagicMock())
     def test_refresh_fan_drawer_status_fan_drawer_get_name_not_impl(self):