Change network driver test to use non-default driver.

This test case was changed with the Swarm removal to use a default
network driver as the provided setting.
This does not distinguish between the default and the provided, which
would provide better coverage.

Change-Id: Ie8d0ad5a9478a6c870a3d15a0be94913cf36d2da

Author: dalees

magnum/tests/unit/api/controllers/v1/test_cluster_template.py

@@ -831,7 +831,7 @@ def _test_create_cluster_template_network_driver_attr(
 
     def test_create_cluster_template_with_network_driver(self):
         cluster_template_dict = {'coe': 'kubernetes',
-                                 'network_driver': 'flannel'}
+                                 'network_driver': 'calico'}
         config_dict = {}    # Default config
         expect_errors_flag = False
         expect_default_driver_flag = False