Fix transfer execution trigger on cron schedule

Fixes the `shutdown_instances` keyword argument name.

coriolis/tests/transfer_cron/rpc/test_server.py

@@ -31,7 +31,7 @@ class TriggerTransferTestCase(test_base.CoriolisBaseTestCase):
 
         mock_conductor_client.execute_transfer_tasks.assert_called_once_with(
             mock.sentinel.ctxt, mock.sentinel.transfer_id,
-            shutdown_instance=False, auto_deploy=False)
+            shutdown_instances=False, auto_deploy=False)
 
         self.assertEqual(
             result, 'Execution %s for Transfer %s' % (

coriolis/transfer_cron/rpc/server.py

@@ -21,7 +21,7 @@ def _trigger_transfer(ctxt, conductor_client, transfer_id, shutdown_instance,
                       auto_deploy):
     try:
         execution = conductor_client.execute_transfer_tasks(
-            ctxt, transfer_id, shutdown_instance=shutdown_instance,
+            ctxt, transfer_id, shutdown_instances=shutdown_instance,
             auto_deploy=auto_deploy)
         result_msg = 'Execution %s for Transfer %s' % (
             execution.get('id'), execution.get('action_id'))