resource/aws_ssm_parameter: ForceNew on ssm_parameter rename

Fixes: #1008

There doesn't seem to be a way to change the name of an AWS SSM
Parameter. Therefore, it should be marked as ForceNew.

```
% make testacc TEST=./aws TESTARGS='-run=TestAccAWSSSMParameter_'
==> Checking that code complies with gofmt requirements...
TF_ACC=1 go test ./aws -v -run=TestAccAWSSSMParameter_ -timeout 120m
=== RUN   TestAccAWSSSMParameter_basic
--- PASS: TestAccAWSSSMParameter_basic (25.06s)
=== RUN   TestAccAWSSSMParameter_update
--- PASS: TestAccAWSSSMParameter_update (43.21s)
=== RUN   TestAccAWSSSMParameter_changeNameForcesNew
--- PASS: TestAccAWSSSMParameter_changeNameForcesNew (40.84s)
=== RUN   TestAccAWSSSMParameter_secure
--- PASS: TestAccAWSSSMParameter_secure (37.90s)
=== RUN   TestAccAWSSSMParameter_secure_with_key
--- PASS: TestAccAWSSSMParameter_secure_with_key (73.26s)
PASS
ok  	github.com/terraform-providers/terraform-provider-aws/aws	220.297s
```

aws/resource_aws_ssm_parameter.go

@@ -21,6 +21,7 @@ func resourceAwsSsmParameter() *schema.Resource {
 			"name": {
 				Type:     schema.TypeString,
 				Required: true,
+				ForceNew: true,
 			},
 			"type": {
 				Type:         schema.TypeString,

aws/resource_aws_ssm_parameter_test.go

@@ -50,6 +50,25 @@ func TestAccAWSSSMParameter_update(t *testing.T) {
 	})
 }
 
+func TestAccAWSSSMParameter_changeNameForcesNew(t *testing.T) {
+	name := acctest.RandString(10)
+	resource.Test(t, resource.TestCase{
+		PreCheck:     func() { testAccPreCheck(t) },
+		Providers:    testAccProviders,
+		CheckDestroy: testAccCheckAWSSSMParameterDestroy,
+		Steps: []resource.TestStep{
+			{
+				Config: testAccAWSSSMParameterBasicConfig(name, "bar"),
+			},
+			{
+				Config:             testAccAWSSSMParameterBasicConfigChangeName(name, "baz1"),
+				PlanOnly:           true,
+				ExpectNonEmptyPlan: true,
+			},
+		},
+	})
+}
+
 func TestAccAWSSSMParameter_secure(t *testing.T) {
 	name := acctest.RandString(10)
 	resource.Test(t, resource.TestCase{
@@ -183,6 +202,16 @@ resource "aws_ssm_parameter" "foo" {
 `, rName, value)
 }
 
+func testAccAWSSSMParameterBasicConfigChangeName(rName string, value string) string {
+	return fmt.Sprintf(`
+resource "aws_ssm_parameter" "foo" {
+  name  = "test_parameter-%s"
+  type  = "String"
+  value = "%s"
+}
+`, rName, value)
+}
+
 func testAccAWSSSMParameterBasicConfigOverwrite(rName string, value string) string {
 	return fmt.Sprintf(`
 resource "aws_ssm_parameter" "foo" {