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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

```

- Corresponds to the C(--reserve-cpu) option of C(docker service create).
        type: float
      memory:
        description:
          - "Service memory reservation in format C(<number>[<unit>]). Number is a positive integer.
            Unit can be C(B) (byte), C(K) (kibibyte, 1024B), C(M) (mebibyte), C(G) (gibibyte),
            C(T) (tebibyte), or C(P) (pebibyte)."
          - C(0) equals no reservation.
          - Omitting the unit defaults to bytes.
          - Corresponds to the C(--reserve-memory) option of C(docker service create).
        type: str
    type: dict
    version_added: "2.8"
  reserve_cpu:
    description:
      - Service CPU reservation. C(0) equals no reservation.
      - Corresponds to the C(--reserve-cpu) option of C(docker service create).
      - Deprecated in 2.8, will be removed in 2.12. Use parameter C(reservations.cpus) instead.
    type: float
  reserve_memory:
    description:
      - "Service memory reservation in format C(<number>[<unit>]). Number is a positive integer.
        Unit can be C(B) (byte), C(K) (kibibyte, 1024B), C(M) (mebibyte), C(G) (gibibyte),
        C(T) (tebibyte), or C(P) (pebibyte)."
      - C(0) equals no reservation.
      - Omitting the unit defaults to bytes.
      - Corresponds to the C(--reserve-memory) option of C(docker service create).
      - Deprecated in 2.8, will be removed in 2.12. Use parameter C(reservations.memory) instead.
    type: str
  resolve_image: