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##### SUMMARY
<!--- Explain the problem briefly below -->
In docker_swarm_service module in ansible, if we are specifying mount option as tmpfs, it is required to set src. But for docker service create, src is not supported for tmpfs.
##### 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_swarm_service

##### ANSIBLE VERSION
<!--- Paste verbatim output from "ansible --version" between quotes -->
```paste below
ansible 2.8.4
  config file = /home/vani/Projects/voody/ansible/ansible.cfg
  configured module search path = ['/home/vani/.ansible/plugins/modules', '/usr/share/ansible/plugins/modules']
  ansible python module location = /usr/local/lib/python3.6/dist-packages/ansible
  executable location = /usr/local/bin/ansible
  python version = 3.6.8 (default, Aug 20 2019, 17:12:48) [GCC 8.3.0]

```

##### CONFIGURATION
<!--- Paste verbatim output from "ansible-config dump --only-changed" between quotes -->
```paste below
ANSIBLE_NOCOWS(/home/user/Projects/ansible/ansible.cfg) = True
DEFAULT_STDOUT_CALLBACK(/home/user/Projects/ansible/ansible.cfg) = yaml
```

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


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

<!--- Paste example playbooks or commands between quotes below -->
```yaml

```

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##### EXPECTED RESULTS
<!--- Describe what you expected to happen when running the steps above -->


##### ACTUAL RESULTS
<!--- Describe what actually happened. If possible run with extra verbosity (-vvvv) -->

<!--- Paste verbatim command output between quotes -->
```paste below

```

extends_documentation_fragment:
  - docker
  - docker.docker_py_2_documentation
requirements:
  - "L(Docker SDK for Python,https://docker-py.readthedocs.io/en/stable/) >= 2.0.2"
  - "Docker API >= 1.24"
notes:
  - "Images will only resolve to the latest digest when using Docker API >= 1.30 and Docker SDK for Python >= 3.2.0.
     When using older versions use C(force_update: true) to trigger the swarm to resolve a new image."
'''
RETURN = '''
swarm_service:
  returned: always
  type: dict
  description:
    - Dictionary of variables representing the current state of the service.
      Matches the module parameters format.
    - Note that facts are not part of registered vars but accessible directly.
    - Note that before Ansible 2.7.9, the return variable was documented as C(ansible_swarm_service),
      while the module actually returned a variable called C(ansible_docker_service). The variable
      was renamed to C(swarm_service) in both code and documentation for Ansible 2.7.9 and Ansible 2.8.0.
      In Ansible 2.7.x, the old name C(ansible_docker_service) can still be used.
  sample: '{
    "args": [
      "3600"
    ],
    "command": [
      "sleep"
    ],
    "configs": null,