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/setup/manifest-olt-voltha.json b/src/test/setup/manifest-olt-voltha.json
index 276e480..7629045 100644
--- a/src/test/setup/manifest-olt-voltha.json
+++ b/src/test/setup/manifest-olt-voltha.json
@@ -8,5 +8,6 @@
     "onos_image": "onosproject/onos:latest",
     "log_level" : "INFO",
     "jvm_heap_size" : "1G",
-    "karaf_version" : "3.0.5"
+    "karaf_version" : "3.0.5",
+    "voltha_enable" : true
 }