zones: initial implementation of Zones interface

Author: nicolehanjing

pkg/providers/v2/instances.go

@@ -232,12 +232,12 @@ func getInstanceByProviderID(ctx context.Context, providerID string, ec2Client E
 	}
 
 	if len(instances) > 1 {
-		return nil, fmt.Errorf("getInstance: multiple instances found")
+		return nil, errors.New("getInstance: multiple instances found")
 	}
 
 	state := instances[0].State.Name
 	if *state == ec2.InstanceStateNameTerminated {
-		return nil, fmt.Errorf("instance %v is terminated", instances[0].InstanceId)
+		return nil, cloudprovider.InstanceNotFound
 	}
 
 	return instances[0], nil