Introduce: voltha_enable config to run tests with voltha environment enabled.
This is needed if one is running voltha externally and wants to run cord-tester from another node to test voltha.
(subscriber side pc to talk to olt connected voltha node)
Otherwise it defaults to enabled if voltha_loc is set (running locally with voltha).

Change-Id: I6956b6b20c3452e5acf7a00411ac1ff4a7eaf199
diff --git a/src/test/utils/TestManifest.py b/src/test/utils/TestManifest.py
index 26c5130..9d4825b 100644
--- a/src/test/utils/TestManifest.py
+++ b/src/test/utils/TestManifest.py
@@ -52,6 +52,7 @@
             self.karaf_version = args.karaf
             self.voltha_loc = args.voltha_loc
             self.voltha_intf = args.voltha_intf
+            self.voltha_enable = args.voltha_enable
         else:
             with open(self.manifest, 'r') as fd:
                 data = json.load(fd)
@@ -80,3 +81,7 @@
             self.karaf_version = data.get('karaf_version', '3.0.8')
             self.voltha_loc = data.get('voltha_loc', '')
             self.voltha_intf = data.get('voltha_intf', 'eth0')
+            voltha_enable = False
+            if self.voltha_loc:
+                voltha_enable = True
+            self.voltha_enable = data.get('voltha_enable', voltha_enable)