Fix transitions for image_download and activation

Change-Id: I713ada52eef9d275c7d7596026e178c7382e8335
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)