make groups magic var dependant on inventory (#28677)

* make groups magic var dependant on inventory

it was overtly restricted by 'host'
minor fixes to test_var_manager.py, need to test other values also

* pepe hates extra blank line

lib/ansible/vars/manager.py

@@ -457,10 +457,6 @@ class VariableManager:
         variables['playbook_dir'] = os.path.abspath(self._loader.get_basedir())
         variables['ansible_playbook_python'] = sys.executable
 
-        if host:
-            # host already provides some magic vars via host.get_vars()
-            if self._inventory:
-                variables['groups'] = self._inventory.get_groups_dict()
         if play:
             variables['role_names'] = [r._role_name for r in play.roles]
 
@@ -471,6 +467,7 @@ class VariableManager:
                 variables['role_uuid'] = text_type(task._role._uuid)
 
         if self._inventory is not None:
+            variables['groups'] = self._inventory.get_groups_dict()
             if play:
                 templar = Templar(loader=self._loader)
                 if templar.is_template(play.hosts):

test/units/vars/test_variable_manager.py

@@ -50,14 +50,12 @@ class TestVariableManager(unittest.TestCase):
 
         mock_inventory = MagicMock()
         v = VariableManager(loader=fake_loader, inventory=mock_inventory)
-        vars = v.get_vars(use_cache=False)
-
-        # FIXME: not sure why we remove all and only test playbook_dir
-        for remove in ['omit', 'vars', 'ansible_version', 'ansible_check_mode', 'ansible_playbook_python']:
-            if remove in vars:
-                del vars[remove]
+        variables = v.get_vars(use_cache=False)
 
-        self.assertEqual(vars, dict(playbook_dir=os.path.abspath('.')))
+        # Check var manager expected values,  never check: ['omit', 'vars']
+        # FIXME:  add the following ['ansible_version', 'ansible_playbook_python', 'groups']
+        for varname, value in (('playbook_dir', os.path.abspath('.')), ):
+            self.assertEqual(variables[varname], value)
 
     def test_variable_manager_extra_vars(self):
         fake_loader = DictDataLoader({})