<!--- Verify first that your issue is not already reported on GitHub -->
<!--- Also test if the latest release and devel branch are affected too -->
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##### SUMMARY
`openssh_keypair` seem to report changed in cases where it shouldn't

##### ISSUE TYPE
- Bug Report

##### COMPONENT NAME
<!--- Write the short name of the module, plugin, task or feature below, use your best guess if unsure -->
openssh_keypair

##### ANSIBLE VERSION
<!--- Paste verbatim output from "ansible --version" between quotes -->
```paste below
ansible 2.9.1
  config file = None
  configured module search path = ['/home/florian/.ansible/plugins/modules', '/usr/share/ansible/plugins/modules']
  ansible python module location = /home/florian/.local/pipx/venvs/ansible/lib64/python3.7/site-packages/ansible
  executable location = /home/florian/.local/bin/ansible
  python version = 3.7.5 (default, Oct 17 2019, 12:16:48) [GCC 9.2.1 20190827 (Red Hat 9.2.1-1)]
```

##### CONFIGURATION
<!--- Paste verbatim output from "ansible-config dump --only-changed" between quotes -->
```paste below
ANSIBLE_NOCOWS(env: ANSIBLE_NOCOWS) = True
```

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

Debian Sid in a docker container, see playbook below


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

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

- hosts: localhost
  gather_facts: no

  tasks:
    - docker_container:  name=testing_debian state=started image=debian:sid command="sleep infinity"
    - add_host: name=testing_debian ansible_connection=docker

- hosts: testing_debian
  gather_facts: no

  tasks:
    # Ensure we start from a consistent state
    - raw: "apt -y update && apt -y install python openssh-client"
    - file: path=/tmp/key state=absent
    - file: path=/tmp/key.pub state=absent

    # full reproducer here

    - openssh_keypair: path=/tmp/key comment=test type=ed25519 
    - openssh_keypair: path=/tmp/key comment=test type=ed25519 
```

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

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

I'd expect the second `openssh_keypair` task to report unchanged.


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

Both tasks show up as changed:

<!--- Paste verbatim command output between quotes -->
```paste below
TASK [file] **********************************************************************************************************************************************************************************************************************************
[WARNING]: Platform linux on host testing_debian is using the discovered Python interpreter at /usr/bin/python, but future installation of another Python interpreter could change this. See
https://docs.ansible.com/ansible/2.9/reference_appendices/interpreter_discovery.html for more information.

ok: [testing_debian] => {"ansible_facts": {"discovered_interpreter_python": "/usr/bin/python"}, "changed": false, "path": "/tmp/key", "state": "absent"}

TASK [file] **********************************************************************************************************************************************************************************************************************************
ok: [testing_debian] => {"changed": false, "path": "/tmp/key.pub", "state": "absent"}

TASK [openssh_keypair] ***********************************************************************************************************************************************************************************************************************
changed: [testing_debian] => {"changed": true, "comment": "test", "filename": "/tmp/key", "fingerprint": "SHA256:k7zoCrUKcwjfvSsKSr+zElJL5wGgCbmNsgGdD4qXp6o", "public_key": "ssh-ed25519 AAAAC3NzaC1lZDI1NTE5AAAAIJ5JTc62+6h0NlqM0r5pranKV3kXS7+XbzO9ZPeY2f36 test", "size": 256, "type": "ed25519"}

TASK [openssh_keypair] ***********************************************************************************************************************************************************************************************************************
changed: [testing_debian] => {"changed": true, "comment": "test", "filename": "/tmp/key", "fingerprint": "SHA256:k7zoCrUKcwjfvSsKSr+zElJL5wGgCbmNsgGdD4qXp6o", "public_key": "ssh-ed25519 AAAAC3NzaC1lZDI1NTE5AAAAIJ5JTc62+6h0NlqM0r5pranKV3kXS7+XbzO9ZPeY2f36 test", "size": 256, "type": "ed25519"}
```

size:
        description:
            - "Specifies the number of bits in the private key to create. For RSA keys, the minimum size is 1024 bits and the default is 4096 bits.
              Generally, 2048 bits is considered sufficient.  DSA keys must be exactly 1024 bits as specified by FIPS 186-2.
              For ECDSA keys, size determines the key length by selecting from one of three elliptic curve sizes: 256, 384 or 521 bits.
              Attempting to use bit lengths other than these three values for ECDSA keys will cause this module to fail.
              Ed25519 keys have a fixed length and the size will be ignored."
        type: int
    type:
        description:
            - "The algorithm used to generate the SSH private key. C(rsa1) is for protocol version 1.
              C(rsa1) is deprecated and may not be supported by every version of ssh-keygen."
        type: str
        default: rsa
        choices: ['rsa', 'dsa', 'rsa1', 'ecdsa', 'ed25519']
    force:
        description:
            - Should the key be regenerated even if it already exists
        type: bool
        default: false
    path:
        description:
            - Name of the files containing the public and private key. The file containing the public key will have the extension C(.pub).
        type: path
        required: true
    comment:
        description:
            - Provides a new comment to the public key. When checking if the key is in the correct state this will be ignored.
        type: str
        version_added: "2.9"