<!--- Verify first that your issue is not already reported on GitHub -->
<!--- Also test if the latest release and devel branch are affected too -->
<!--- Complete *all* sections as described, this form is processed automatically -->

##### SUMMARY
<!--- Explain the problem briefly below -->
The module docker_login save the config.json with 644 permission instead of 600 (default by docker login command)
##### ISSUE TYPE
- Bug Report

##### COMPONENT NAME
<!--- Write the short name of the module, plugin, task or feature below, use your best guess if unsure -->
docker_login
##### ANSIBLE VERSION
<!--- Paste verbatim output from "ansible --version" between quotes -->
```paste below
ansible 2.8.3
  config file = /etc/ansible/ansible.cfg
  configured module search path = [u'/home/gael/.ansible/plugins/modules', u'/usr/share/ansible/plugins/modules']
  ansible python module location = /usr/lib/python2.7/dist-packages/ansible
  executable location = /usr/bin/ansible
  python version = 2.7.12 (default, Dec  4 2017, 14:50:18) [GCC 5.4.0 20160609]
```

##### CONFIGURATION
<!--- Paste verbatim output from "ansible-config dump --only-changed" between quotes -->
```paste below

```

##### OS / ENVIRONMENT
<!--- Provide all relevant information below, e.g. target OS versions, network device firmware, etc. -->
Ubuntu 18.04 server

##### STEPS TO REPRODUCE
<!--- Describe exactly how to reproduce the problem, using a minimal test-case -->

<!--- Paste example playbooks or commands between quotes below -->
```yaml
- name: Log into private registry and force re-authorization
  docker_login:
    registry: "{{ registry_host }}"
    username: "{{ registry_user }}"
    password: "{{ vault_registry_password }}"
```

<!--- HINT: You can paste gist.github.com links for larger files -->

##### EXPECTED RESULTS
<!--- Describe what you expected to happen when running the steps above -->
ll /root/.docker/config.json 
-rw------- 1 root root 181 Jan 10 10:53 /root/.docker/config.json

##### ACTUAL RESULTS
<!--- Describe what actually happened. If possible run with extra verbosity (-vvvv) -->
ll /root/.docker/config.json 
-rw-r--r-- 1 root root 181 Jan 10 10:53 /root/.docker/config.json
<!--- Paste verbatim command output between quotes -->
```paste below

```

def __init__(self, client, results):
        super(LoginManager, self).__init__()
        self.client = client
        self.results = results
        parameters = self.client.module.params
        self.check_mode = self.client.check_mode
        self.registry_url = parameters.get('registry_url')
        self.username = parameters.get('username')
        self.password = parameters.get('password')
        self.email = parameters.get('email')
        self.reauthorize = parameters.get('reauthorize')
        self.config_path = parameters.get('config_path')
        self.state = parameters.get('state')
    def run(self):
        '''
        Do the actuall work of this task here. This allows instantiation for partial
        testing.
        '''
        if self.state == 'present':
            self.login()
        else:
            self.logout()
    def fail(self, msg):
        self.client.fail(msg)
    def login(self):