[VOL-3117] Read KV store data path prefix from an environment variable

- voltha-lib-go reads the KVStoreDataPrefix from env variable, so removed the command-line flag in voltha-go
- also removed unused corepair topic flag
Change-Id: Ibe8403bf187126b587a92cd9c58aa6d923f84cd0
diff --git a/rw_core/core/device/logical_agent_test.go b/rw_core/core/device/logical_agent_test.go
index 77c4b7c..2649ee4 100644
--- a/rw_core/core/device/logical_agent_test.go
+++ b/rw_core/core/device/logical_agent_test.go
@@ -454,7 +454,7 @@
 
 func (lda *LDATest) startCore(inCompeteMode bool) {
 	cfg := config.NewRWCoreFlags()
-	cfg.CorePairTopic = "rw_core"
+	cfg.CoreTopic = "rw_core"
 	cfg.DefaultRequestTimeout = lda.defaultTimeout
 	cfg.KVStorePort = lda.kvClientPort
 	cfg.InCompetingMode = inCompeteMode
@@ -471,8 +471,7 @@
 		Host:                    cfg.KVStoreHost,
 		Port:                    cfg.KVStorePort,
 		Timeout:                 cfg.KVStoreTimeout,
-		LivenessChannelInterval: cfg.LiveProbeInterval / 2,
-		PathPrefix:              cfg.KVStoreDataPrefix}
+		LivenessChannelInterval: cfg.LiveProbeInterval / 2}
 	lda.kmp = kafka.NewInterContainerProxy(
 		kafka.InterContainerHost(cfg.KafkaAdapterHost),
 		kafka.InterContainerPort(cfg.KafkaAdapterPort),
@@ -484,7 +483,7 @@
 	proxy := model.NewDBPath(backend)
 	adapterMgr := adapter.NewAdapterManager(proxy, lda.coreInstanceID, lda.kClient)
 
-	lda.deviceMgr, lda.logicalDeviceMgr = NewManagers(proxy, adapterMgr, lda.kmp, endpointMgr, cfg.CorePairTopic, lda.coreInstanceID, cfg.DefaultCoreTimeout)
+	lda.deviceMgr, lda.logicalDeviceMgr = NewManagers(proxy, adapterMgr, lda.kmp, endpointMgr, cfg.CoreTopic, lda.coreInstanceID, cfg.DefaultCoreTimeout)
 	if err = lda.kmp.Start(); err != nil {
 		logger.Fatal("Cannot start InterContainerProxy")
 	}