Always return True/False from is_state and is_state_attr (#7138)

* Always return True/False from is_state and is_state_attr

These functions are documented to always return True/False but the
short-circuit evaluation would return None if the entity_id did not exist.

* Reword into a single statement

homeassistant/core.py

@@ -648,7 +648,7 @@ class StateMachine(object):
         Async friendly.
         """
         state_obj = self.get(entity_id)
-        return state_obj and state_obj.state == state
+        return state_obj is not None and state_obj.state == state
 
     def is_state_attr(self, entity_id, name, value):
         """Test if entity exists and has a state attribute set to value.
@@ -656,7 +656,8 @@ class StateMachine(object):
         Async friendly.
         """
         state_obj = self.get(entity_id)
-        return state_obj and state_obj.attributes.get(name, None) == value
+        return state_obj is not None and \
+            state_obj.attributes.get(name, None) == value
 
     def remove(self, entity_id):
         """Remove the state of an entity.

tests/helpers/test_template.py

@@ -314,6 +314,11 @@ class TestHelpersTemplate(unittest.TestCase):
             """, self.hass)
         self.assertEqual('yes', tpl.render())
 
+        tpl = template.Template("""
+{{ is_state("test.noobject", "available") }}
+            """, self.hass)
+        self.assertEqual('False', tpl.render())
+
     def test_is_state_attr(self):
         """Test is_state_attr method."""
         self.hass.states.set('test.object', 'available', {'mode': 'on'})
@@ -322,6 +327,11 @@ class TestHelpersTemplate(unittest.TestCase):
                 """, self.hass)
         self.assertEqual('yes', tpl.render())
 
+        tpl = template.Template("""
+{{ is_state_attr("test.noobject", "mode", "on") }}
+                """, self.hass)
+        self.assertEqual('False', tpl.render())
+
     def test_states_function(self):
         """Test using states as a function."""
         self.hass.states.set('test.object', 'available')