ElastiCache cluster read tolerates removed cluster.

Previously it would fail if a Terraform-managed ElastiCache cluster were
deleted outside of Terraform. Now it marks it as deleted in the state so that
Terraform can know it doesn't need to be destroyed, and can potentially
recreate it if asked.

builtin/providers/aws/resource_aws_elasticache_cluster.go

@@ -241,6 +241,12 @@ func resourceAwsElasticacheClusterRead(d *schema.ResourceData, meta interface{})
 
 	res, err := conn.DescribeCacheClusters(req)
 	if err != nil {
+		if eccErr, ok := err.(awserr.Error); ok && eccErr.Code() == "CacheClusterNotFound" {
+			log.Printf("[WARN] ElastiCache Cluster (%s) not found", d.Id())
+			d.SetId("")
+			return nil
+		}
+
 		return err
 	}