Remove get_all method from servicegroup API

Change Idc0dfbbe1887e11166acb7d989dd5466751761af removed
get_all method from mc and db drivers, and made this
method private in zk driver.

Now no one of servicegroup drivers (mc, db, zk) doesn't
implement method get_all. And it's very confusing.

This method used nowhere so it should be removed.

Closes-Bug: #1502107

Change-Id: Ie56d15f61aa61e3bd05c77eab52c65d557de5d8b

nova/servicegroup/api.py

@@ -90,9 +90,3 @@ class API(object):
             return False
 
         return self._driver.is_up(member)
-
-    def get_all(self, group_id):
-        """Returns ALL members of the given group."""
-        LOG.debug('Returns ALL members of the [%s] '
-                  'ServiceGroup', group_id)
-        return self._driver.get_all(group_id)

nova/tests/unit/servicegroup/test_api.py

@@ -40,16 +40,6 @@ class ServiceGroupApiTestCase(test.NoDBTestCase):
         self.assertIsNone(result)
         self.driver.join.assert_called_with(member, group, None)
 
-    def test_get_all(self):
-        result = "fake response"
-        group_id = 1
-
-        self.driver.get_all = mock.MagicMock(return_value=result)
-
-        members = self.servicegroup_api.get_all(group_id)
-        self.assertEqual(members, result)
-        self.driver.get_all.assert_called_with(group_id)
-
     def test_service_is_up(self):
         """"""
         member = {"host": "fake-host",