SEBA-902 single-olt tests;
Pin protoc-gen-go to 1.3.2 to resolve compatibility issue;
Run go mod tidy / go mod vendor on importer;
Add Go Module support to demotest

Change-Id: Ifde824fc9a6317b0adc1e12bea54ee1f9b788906
diff --git a/vendor/github.com/Shopify/sarama/client.go b/vendor/github.com/Shopify/sarama/client.go
index e5b3557..057a57a 100644
--- a/vendor/github.com/Shopify/sarama/client.go
+++ b/vendor/github.com/Shopify/sarama/client.go
@@ -17,9 +17,15 @@
 	// altered after it has been created.
 	Config() *Config
 
-	// Controller returns the cluster controller broker. Requires Kafka 0.10 or higher.
+	// Controller returns the cluster controller broker. It will return a
+	// locally cached value if it's available. You can call RefreshController
+	// to update the cached value. Requires Kafka 0.10 or higher.
 	Controller() (*Broker, error)
 
+	// RefreshController retrieves the cluster controller from fresh metadata
+	// and stores it in the local cache. Requires Kafka 0.10 or higher.
+	RefreshController() (*Broker, error)
+
 	// Brokers returns the current set of active brokers as retrieved from cluster metadata.
 	Brokers() []*Broker
 
@@ -193,7 +199,6 @@
 func (client *client) InitProducerID() (*InitProducerIDResponse, error) {
 	var err error
 	for broker := client.any(); broker != nil; broker = client.any() {
-
 		req := &InitProducerIDRequest{}
 
 		response, err := broker.InitProducerID(req)
@@ -487,6 +492,35 @@
 	return controller, nil
 }
 
+// deregisterController removes the cached controllerID
+func (client *client) deregisterController() {
+	client.lock.Lock()
+	defer client.lock.Unlock()
+	delete(client.brokers, client.controllerID)
+}
+
+// RefreshController retrieves the cluster controller from fresh metadata
+// and stores it in the local cache. Requires Kafka 0.10 or higher.
+func (client *client) RefreshController() (*Broker, error) {
+	if client.Closed() {
+		return nil, ErrClosedClient
+	}
+
+	client.deregisterController()
+
+	if err := client.refreshMetadata(); err != nil {
+		return nil, err
+	}
+
+	controller := client.cachedController()
+	if controller == nil {
+		return nil, ErrControllerNotAvailable
+	}
+
+	_ = controller.Open(client.conf)
+	return controller, nil
+}
+
 func (client *client) Coordinator(consumerGroup string) (*Broker, error) {
 	if client.Closed() {
 		return nil, ErrClosedClient