resource/aws_ssm_parameter: ForceNew on ssm_parameter rename (#1022)

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 +50,27 @@ func TestAccAWSSSMParameter_update(t *testing.T) {
 	})
 }
 
+func TestAccAWSSSMParameter_changeNameForcesNew(t *testing.T) {
+	before := acctest.RandString(10)
+	after := acctest.RandString(10)
+	resource.Test(t, resource.TestCase{
+		PreCheck:     func() { testAccPreCheck(t) },
+		Providers:    testAccProviders,
+		CheckDestroy: testAccCheckAWSSSMParameterDestroy,
+		Steps: []resource.TestStep{
+			{
+				Config: testAccAWSSSMParameterBasicConfig(before, "bar"),
+			},
+			{
+				Config: testAccAWSSSMParameterBasicConfig(after, "bar"),
+				Check: resource.ComposeTestCheckFunc(
+					testAccCheckAWSSSMParameterDestroyed(before),
+				),
+			},
+		},
+	})
+}
+
 func TestAccAWSSSMParameter_secure(t *testing.T) {
 	name := acctest.RandString(10)
 	resource.Test(t, resource.TestCase{
@@ -147,6 +168,29 @@ func testAccCheckAWSSSMParameterType(n string, v string) resource.TestCheckFunc
 	}
 }
 
+func testAccCheckAWSSSMParameterDestroyed(name string) resource.TestCheckFunc {
+	return func(s *terraform.State) error {
+		conn := testAccProvider.Meta().(*AWSClient).ssmconn
+
+		paramInput := &ssm.GetParametersInput{
+			Names: []*string{
+				aws.String(name),
+			},
+		}
+
+		resp, err := conn.GetParameters(paramInput)
+		if err != nil {
+			return err
+		}
+
+		if len(resp.Parameters) > 0 {
+			return fmt.Errorf("Expected AWS SSM Parameter to be gone, but was still found")
+		}
+
+		return nil
+	}
+}
+
 func testAccCheckAWSSSMParameterDestroy(s *terraform.State) error {
 	conn := testAccProvider.Meta().(*AWSClient).ssmconn