Fail cloudformation operation when it is not completed successfully

When cloudformation operation is successfully submitted but some step
during stack creation or update fails, operation result should be
failed=True.

**What version of ansible you are using (ansible --version):**

ansible 1.4 (devel 9b5fb9ad6b) last updated 2013/09/30 15:44:30 (GMT +200)

**Steps to reproduce the problem:**

Use cloudformation module with template that can be successfully submitted bud fails during creation.

aws.yml:
```yaml
- hosts: vpc
  gather_facts: no
  connection: local
  tasks:
    - name: create cloudformation stack
      cloudformation: >
        stack_name=TestStack
        template=cf_test.json
        region={{ region }}
        state=present
      args:
        template_parameters: {}
```
cf_test.json ("Tags" property is "key" instead of "Key"):
```json
{
  "AWSTemplateFormatVersion": "2010-09-09",
  "Description": "Virtual Private Cloud",
  "Resources": {
    "VPC01": {
      "Type": "AWS::EC2::VPC",
      "Properties": {
        "CidrBlock": "10.1.0.0/16",
        "Tags": [
          { "key": "test", "Value": "xxx" }
        ]
      }
    }
  }
}
```

Run:
```sh
ansible-playbook aws.yml -i vpc,
```

**Expected results:**

Task result is failed=True

**Actual results:**

Task result is changed=True (disable_rollback=no) or changed=False (disable_rollback=yes)