[VOL-2782] Update go.mod of voltha-go,open-olt-adapter,ofagent-go and voltctl to be compatible with latest version of voltha-lig-go

Change-Id: Iafd5ee70ae0f17db141cb5d7fc25380c3482274a
diff --git a/vendor/github.com/opencord/voltha-lib-go/v3/pkg/config/configmanager.go b/vendor/github.com/opencord/voltha-lib-go/v3/pkg/config/configmanager.go
index 462b743..441c488 100644
--- a/vendor/github.com/opencord/voltha-lib-go/v3/pkg/config/configmanager.go
+++ b/vendor/github.com/opencord/voltha-lib-go/v3/pkg/config/configmanager.go
@@ -33,7 +33,7 @@
 
 const (
 	defaultkvStoreConfigPath = "config"
-	kvStoreDataPathPrefix    = "/service/voltha"
+	kvStoreDataPathPrefix    = "service/voltha"
 	kvStorePathSeparator     = "/"
 )
 
@@ -59,6 +59,10 @@
 	Delete
 )
 
+func (ce ChangeEvent) String() string {
+	return [...]string{"Put", "Delete"}[ce]
+}
+
 // ConfigChangeEvent represents config for the events recieved from watch
 // For example,ChangeType is Put ,ConfigAttribute default
 type ConfigChangeEvent struct {
@@ -207,6 +211,25 @@
 	}
 }
 
+// Retrieves value of a specific config key. Value of key is returned in String format
+func (c *ComponentConfig) Retrieve(ctx context.Context, configKey string) (string, error) {
+	key := c.makeConfigPath() + "/" + configKey
+
+	log.Debugw("retrieving-config", log.Fields{"key": key})
+
+	if kvpair, err := c.cManager.backend.Get(ctx, key); err != nil {
+		return "", err
+	} else {
+		if kvpair == nil {
+			return "", fmt.Errorf("config-key-does-not-exist : %s", key)
+		}
+
+		value := strings.Trim(fmt.Sprintf("%s", kvpair.Value), "\"")
+		log.Debugw("retrieved-config", log.Fields{"key": key, "value": value})
+		return value, nil
+	}
+}
+
 func (c *ComponentConfig) RetrieveAll(ctx context.Context) (map[string]string, error) {
 	key := c.makeConfigPath()
 
@@ -233,7 +256,7 @@
 func (c *ComponentConfig) Save(ctx context.Context, configKey string, configValue string) error {
 	key := c.makeConfigPath() + "/" + configKey
 
-	log.Debugw("saving-key", log.Fields{"key": key, "value": configValue})
+	log.Debugw("saving-config", log.Fields{"key": key, "value": configValue})
 
 	//save the data for update config
 	if err := c.cManager.backend.Put(ctx, key, configValue); err != nil {
@@ -246,7 +269,7 @@
 	//construct key using makeConfigPath
 	key := c.makeConfigPath() + "/" + configKey
 
-	log.Debugw("deleting-key", log.Fields{"key": key})
+	log.Debugw("deleting-config", log.Fields{"key": key})
 	//delete the config
 	if err := c.cManager.backend.Delete(ctx, key); err != nil {
 		return err