Enable igmp test to work under voltha.
Also change cordSubscriber voltha test to work with the voltha auto configure.
Import teardown_module as well in other test cases.
The tests that are not supposed to work with voltha or rely on auto configure should set:
VOLTHA_AUTO_CONFIGURE = False
in their test class.

Change-Id: Ibbe60e524d31e7079e0423e9e3c390ee17dee2a7
diff --git a/src/test/utils/CordTestConfig.py b/src/test/utils/CordTestConfig.py
index e57b948..f41d0da 100644
--- a/src/test/utils/CordTestConfig.py
+++ b/src/test/utils/CordTestConfig.py
@@ -78,7 +78,7 @@
     voltha_attrs = dict(host='172.17.0.1',
                         rest_port = 8881,
                         config_fake = False,
-                        olt_type = 'ponsim',
+                        olt_type = 'ponsim_olt',
                         olt_mac = '00:0c:e2:31:12:00',
                         uplink_vlan_map = { 'of:0000000000000001' : '222' }
                         )