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/VolthaCtrl.py b/src/test/utils/VolthaCtrl.py
index 9e9b757..d7ab139 100644
--- a/src/test/utils/VolthaCtrl.py
+++ b/src/test/utils/VolthaCtrl.py
@@ -304,7 +304,7 @@
     return olt_app_file
 
 def voltha_setup(host = '172.17.0.1', rest_port = VolthaCtrl.REST_PORT,
-                 olt_type = 'ponsim', olt_mac = '00:0c:e2:31:12:00',
+                 olt_type = 'ponsim_olt', olt_mac = '00:0c:e2:31:12:00',
                  uplink_vlan_map = VolthaCtrl.UPLINK_VLAN_MAP,
                  config_fake = False, olt_app = None):
 
@@ -318,7 +318,8 @@
         device_id, status = voltha.enable_device(olt_type, olt_mac)
 
     if device_id is None or status is False:
-        voltha.disable_device(device_id)
+        if device_id:
+            voltha.disable_device(device_id)
         return None
 
     switch_map = None