### Description
This is a follow-up to #47. When running the native playbook… a second time, the user will run into the following:
```
TASK [mongo_4_0 : configure replica set] ***************************************
fatal: [localhost]: FAILED! => {"changed": false, "module_stderr": "/root/.ansible/tmp/ansible-tmp-1624872124.1895957-19738-170392710700769/AnsiballZ_mongodb_replica_set:18: DeprecationWarning: the imp module is deprecated in favour of importlib; see the module's documentation for alternative uses\n import imp\nTraceback (most recent call last):\n File \"/tmp/ansible_mongodb_replica_set_payload_bozb8srj/__main__.py\", line 121, in reconfig_replset\n File \"/usr/local/lib/python3.8/dist-packages/pymongo/database.py\", line 738, in command\n return self._command(sock_info, command, slave_ok, value,\n File \"/usr/local/lib/python3.8/dist-packages/pymongo/database.py\", line 626, in _command\n return sock_info.command(\n File \"/usr/local/lib/python3.8/dist-packages/pymongo/pool.py\", line 683, in command\n return command(self, dbname, spec, slave_ok,\n File \"/usr/local/lib/python3.8/dist-packages/pymongo/network.py\", line 159, in command\n helpers._check_command_response(\n File \"/usr/local/lib/python3.8/dist-packages/pymongo/helpers.py\", line 160, in _check_command_response\n raise OperationFailure(errmsg, code, response, max_wire_version)\npymongo.errors.OperationFailure: Support for replication protocol version 0 was removed in MongoDB 4.0. Downgrade to MongoDB version 3.6 and upgrade your protocol version to 1 before upgrading your MongoDB version, full error: {'operationTime': Timestamp(1624872122, 2), 'ok': 0.0, 'errmsg': 'Support for replication protocol version 0 was removed in MongoDB 4.0. Downgrade to MongoDB version 3.6 and upgrade your protocol version to 1 before upgrading your MongoDB version', 'code': 103, 'codeName': 'NewReplicaSetConfigurationIncompatible', '$clusterTime': {'clusterTime': Timestamp(1624872122, 2), 'signature': {'hash': b'\\xaf*\\x8d\\xc2\\x9d\\xc4R>\\xdf\\x1an?\\xe8No\\xbe\\x8b\\x02ho', 'keyId': 6977701412083859460}}}\n\nDuring handling of the above exception, another exception occurred:\n\nTraceback (most recent call last):\n File \"/root/.ansible/tmp/ansible-tmp-1624872124.1895957-19738-170392710700769/AnsiballZ_mongodb_replica_set\", line 114, in <module>\n _ansiballz_main()\n File \"/root/.ansible/tmp/ansible-tmp-1624872124.1895957-19738-170392710700769/AnsiballZ_mongodb_replica_set\", line 106, in _ansiballz_main\n invoke_module(zipped_mod, temp_path, ANSIBALLZ_PARAMS)\n File \"/root/.ansible/tmp/ansible-tmp-1624872124.1895957-19738-170392710700769/AnsiballZ_mongodb_replica_set\", line 49, in invoke_module\n imp.load_module('__main__', mod, module, MOD_DESC)\n File \"/usr/lib/python3.8/imp.py\", line 234, in load_module\n return load_source(name, filename, file)\n File \"/usr/lib/python3.8/imp.py\", line 169, in load_source\n module = _exec(spec, sys.modules[name])\n File \"<frozen importlib._bootstrap>\", line 604, in _exec\n File \"<frozen importlib._bootstrap_external>\", line 783, in exec_module\n File \"<frozen importlib._bootstrap>\", line 219, in _call_with_frames_removed\n File \"/tmp/ansible_mongodb_replica_set_payload_bozb8srj/__main__.py\", line 385, in <module>\n File \"/tmp/ansible_mongodb_replica_set_payload_bozb8srj/__main__.py\", line 269, in update_replset\n File \"/tmp/ansible_mongodb_replica_set_payload_bozb8srj/__main__.py\", line 123, in reconfig_replset\nAttributeError: 'OperationFailure' object has no attribute 'message'\n", "module_stdout": "", "msg": "MODULE FAILURE\nSee stdout/stderr for the exact error", "rc": 1}
```
Originally reported on #ops, [here](https://openedx.slack.com/archives/C08B4LZEZ/p1624873238025800) and [here](https://openedx.slack.com/archives/C08B4LZEZ/p1625104718027800).
### Acceptance criteria
* Running the native playbook a second time does not cause the above failure and does not have any other detectably harmful side effects.
### Estimated effort
4 hours of work by a developer versed in Ansible and Mongo
### Bounties offered
None, yet.