provider/aws: Fix aws_route53_record alias perpetual diff

Fixes #9628
Fixes #9298

When a route53_record alias is updated in the console, AWS prepends
`dualstack.` to the name. This is there incase IPV6 is wanted. It is
exactly the same without it as it is with it

In order to stop perpetual diffs, I introduced a normalizeFunc that will
that tke alias name and strip known issues:

* dualstack
* trailing dot

This normalize fun will continue to grow I'm sure

```
% make testacc TEST=./builtin/providers/aws TESTARGS='-run=TestAccAWSRoute53Record_'                                         ✹
==> Checking that code complies with gofmt requirements...
go generate $(go list ./... | grep -v /terraform/vendor/)
2016/10/29 00:28:12 Generated command/internal_plugin_list.go
TF_ACC=1 go test ./builtin/providers/aws -v -run=TestAccAWSRoute53Record_ -timeout 120m
=== RUN   TestAccAWSRoute53Record_basic
--- PASS: TestAccAWSRoute53Record_basic (124.64s)
=== RUN   TestAccAWSRoute53Record_basic_fqdn
--- PASS: TestAccAWSRoute53Record_basic_fqdn (132.07s)
=== RUN   TestAccAWSRoute53Record_txtSupport
--- PASS: TestAccAWSRoute53Record_txtSupport (134.07s)
=== RUN   TestAccAWSRoute53Record_spfSupport
--- PASS: TestAccAWSRoute53Record_spfSupport (113.36s)
=== RUN   TestAccAWSRoute53Record_generatesSuffix
--- PASS: TestAccAWSRoute53Record_generatesSuffix (112.62s)
=== RUN   TestAccAWSRoute53Record_wildcard
--- PASS: TestAccAWSRoute53Record_wildcard (162.84s)
=== RUN   TestAccAWSRoute53Record_failover
--- PASS: TestAccAWSRoute53Record_failover (126.18s)
=== RUN   TestAccAWSRoute53Record_weighted_basic
--- PASS: TestAccAWSRoute53Record_weighted_basic (121.10s)
=== RUN   TestAccAWSRoute53Record_alias
--- PASS: TestAccAWSRoute53Record_alias (118.14s)
=== RUN   TestAccAWSRoute53Record_s3_alias
--- PASS: TestAccAWSRoute53Record_s3_alias (155.07s)
=== RUN   TestAccAWSRoute53Record_weighted_alias
--- PASS: TestAccAWSRoute53Record_weighted_alias (235.41s)
=== RUN   TestAccAWSRoute53Record_geolocation_basic
^[[C--- PASS: TestAccAWSRoute53Record_geolocation_basic (125.32s)
=== RUN   TestAccAWSRoute53Record_latency_basic
--- PASS: TestAccAWSRoute53Record_latency_basic (122.23s)
=== RUN   TestAccAWSRoute53Record_TypeChange
--- PASS: TestAccAWSRoute53Record_TypeChange (231.98s)
=== RUN   TestAccAWSRoute53Record_empty
--- PASS: TestAccAWSRoute53Record_empty (116.48s)
PASS
ok  	github.com/hashicorp/terraform/builtin/providers/aws	2131.526s
```

Before this fix, I was getting the following by recreating the code in

```
~ aws_route53_record.alias
    alias.1563903989.evaluate_target_health: "true" => "false"
    alias.1563903989.name:                   "9828-recreation-106795730.us-west-2.elb.amazonaws.com." => ""
    alias.1563903989.zone_id:                "Z1H1FL5HABSF5" => ""
    alias.318754017.evaluate_target_health:  "" => "true"
    alias.318754017.name:                    "" => "9828-recreation-106795730.us-west-2.elb.amazonaws.com"
    alias.318754017.zone_id:                 "" => "Z1H1FL5HABSF5"

Plan: 0 to add, 1 to change, 0 to destroy.
```

After this fix:

```

No changes. Infrastructure is up-to-date. This means that Terraform
could not detect any differences between your configuration and
the real physical resources that exist. As a result, Terraform
doesn't need to do anything.

builtin/providers/aws/resource_aws_route53_record.go

@@ -95,8 +95,9 @@ func resourceAwsRoute53Record() *schema.Resource {
 						},
 
 						"name": &schema.Schema{
-							Type:     schema.TypeString,
-							Required: true,
+							Type:      schema.TypeString,
+							Required:  true,
+							StateFunc: normalizeAwsAliasName,
 						},
 
 						"evaluate_target_health": &schema.Schema{
@@ -374,7 +375,7 @@ func resourceAwsRoute53RecordRead(d *schema.ResourceData, meta interface{}) erro
 	}
 
 	if alias := record.AliasTarget; alias != nil {
-		name := strings.TrimSuffix(*alias.DNSName, ".")
+		name := normalizeAwsAliasName(*alias.DNSName)
 		d.Set("alias", []interface{}{
 			map[string]interface{}{
 				"zone_id": *alias.HostedZoneId,
@@ -732,7 +733,7 @@ func expandRecordName(name, zone string) string {
 func resourceAwsRoute53AliasRecordHash(v interface{}) int {
 	var buf bytes.Buffer
 	m := v.(map[string]interface{})
-	buf.WriteString(fmt.Sprintf("%s-", m["name"].(string)))
+	buf.WriteString(fmt.Sprintf("%s-", normalizeAwsAliasName(m["name"].(string))))
 	buf.WriteString(fmt.Sprintf("%s-", m["zone_id"].(string)))
 	buf.WriteString(fmt.Sprintf("%t-", m["evaluate_target_health"].(bool)))
 
@@ -748,3 +749,12 @@ func nilString(s string) *string {
 	}
 	return aws.String(s)
 }
+
+func normalizeAwsAliasName(alias interface{}) string {
+	input := alias.(string)
+	if strings.HasPrefix(input, "dualstack.") {
+		return strings.Replace(input, "dualstack.", "", -1)
+	}
+
+	return strings.TrimRight(input, ".")
+}