[VOL-4290] Voltha go library updates for gRPC migration

Change-Id: I1aa2774beb6b7ed7419bc45aeb53fcae8a8ecda0
diff --git a/vendor/google.golang.org/grpc/health/client.go b/vendor/google.golang.org/grpc/health/client.go
index b43746e..419f060 100644
--- a/vendor/google.golang.org/grpc/health/client.go
+++ b/vendor/google.golang.org/grpc/health/client.go
@@ -33,20 +33,20 @@
 	"google.golang.org/grpc/status"
 )
 
-const maxDelay = 120 * time.Second
-
-var backoffStrategy = backoff.Exponential{MaxDelay: maxDelay}
-var backoffFunc = func(ctx context.Context, retries int) bool {
-	d := backoffStrategy.Backoff(retries)
-	timer := time.NewTimer(d)
-	select {
-	case <-timer.C:
-		return true
-	case <-ctx.Done():
-		timer.Stop()
-		return false
+var (
+	backoffStrategy = backoff.DefaultExponential
+	backoffFunc     = func(ctx context.Context, retries int) bool {
+		d := backoffStrategy.Backoff(retries)
+		timer := time.NewTimer(d)
+		select {
+		case <-timer.C:
+			return true
+		case <-ctx.Done():
+			timer.Stop()
+			return false
+		}
 	}
-}
+)
 
 func init() {
 	internal.HealthCheckFunc = clientHealthCheck
@@ -105,7 +105,7 @@
 				continue retryConnection
 			}
 
-			// As a message has been received, removes the need for backoff for the next retry by reseting the try count.
+			// As a message has been received, removes the need for backoff for the next retry by resetting the try count.
 			tryCnt = 0
 			if resp.Status == healthpb.HealthCheckResponse_SERVING {
 				setConnectivityState(connectivity.Ready)
diff --git a/vendor/google.golang.org/grpc/health/server.go b/vendor/google.golang.org/grpc/health/server.go
index c79f9d2..2262607 100644
--- a/vendor/google.golang.org/grpc/health/server.go
+++ b/vendor/google.golang.org/grpc/health/server.go
@@ -35,7 +35,7 @@
 
 // Server implements `service Health`.
 type Server struct {
-	mu sync.Mutex
+	mu sync.RWMutex
 	// If shutdown is true, it's expected all serving status is NOT_SERVING, and
 	// will stay in NOT_SERVING.
 	shutdown bool
@@ -54,8 +54,8 @@
 
 // Check implements `service Health`.
 func (s *Server) Check(ctx context.Context, in *healthpb.HealthCheckRequest) (*healthpb.HealthCheckResponse, error) {
-	s.mu.Lock()
-	defer s.mu.Unlock()
+	s.mu.RLock()
+	defer s.mu.RUnlock()
 	if servingStatus, ok := s.statusMap[in.Service]; ok {
 		return &healthpb.HealthCheckResponse{
 			Status: servingStatus,
@@ -139,7 +139,7 @@
 // Shutdown sets all serving status to NOT_SERVING, and configures the server to
 // ignore all future status changes.
 //
-// This changes serving status for all services. To set status for a perticular
+// This changes serving status for all services. To set status for a particular
 // services, call SetServingStatus().
 func (s *Server) Shutdown() {
 	s.mu.Lock()
@@ -153,7 +153,7 @@
 // Resume sets all serving status to SERVING, and configures the server to
 // accept all future status changes.
 //
-// This changes serving status for all services. To set status for a perticular
+// This changes serving status for all services. To set status for a particular
 // services, call SetServingStatus().
 func (s *Server) Resume() {
 	s.mu.Lock()