Following https://code.launchpad.net/~aym-frikha/charm-mongodb/+git/charm-mongodb/+merge/406294 and a fix for LP: #1943501, if we deploy 3 units with a replicaset name configured, the leader unit fails the replica-set-relation-changed hook:
Content of mongodb.conf (note no replSet config):
```
# mongodb.conf
dbpath=/var/lib/mongodb
ipv6=true
logpath=/var/log/mongodb/mongodb.log
logappend=true
bind_ip = 0.0.0.0
port = 27017
journal=true
master = true
```
2021-10-12 23:03:12 WARNING unit.mongodb/0.replica-set-relation-changed logger.go:60 Traceback (most recent call last):
2021-10-12 23:03:12 WARNING unit.mongodb/0.replica-set-relation-changed logger.go:60 File "/var/lib/juju/agents/unit-mongodb-0/charm/hooks/replica-set-relation-changed", line 2093, in <module>
2021-10-12 23:03:12 WARNING unit.mongodb/0.replica-set-relation-changed logger.go:60 hooks.execute(sys.argv)
2021-10-12 23:03:12 WARNING unit.mongodb/0.replica-set-relation-changed logger.go:60 File "/var/lib/juju/agents/unit-mongodb-0/charm/hooks/charmhelpers/core/hookenv.py", line 943, in execute
2021-10-12 23:03:12 WARNING unit.mongodb/0.replica-set-relation-changed logger.go:60 self._hooks[hook_name]()
2021-10-12 23:03:12 WARNING unit.mongodb/0.replica-set-relation-changed logger.go:60 File "/var/lib/juju/agents/unit-mongodb-0/charm/hooks/replica-set-relation-changed", line 1496, in replica_set_relation_changed
2021-10-12 23:03:12 WARNING unit.mongodb/0.replica-set-relation-changed logger.go:60 init_replset()
2021-10-12 23:03:12 WARNING unit.mongodb/0.replica-set-relation-changed logger.go:60 File "/var/lib/juju/agents/unit-mongodb-0/charm/hooks/replica-set-relation-changed", line 661, in init_replset
2021-10-12 23:03:12 WARNING unit.mongodb/0.replica-set-relation-changed logger.go:60 r = run_admin_command(c, "replSetGetStatus")
2021-10-12 23:03:12 WARNING unit.mongodb/0.replica-set-relation-changed logger.go:60 File "/var/lib/juju/agents/unit-mongodb-0/charm/hooks/replica-set-relation-changed", line 695, in run_admin_command
2021-10-12 23:03:12 WARNING unit.mongodb/0.replica-set-relation-changed logger.go:60 return client.admin.command(cmdstr)
2021-10-12 23:03:12 WARNING unit.mongodb/0.replica-set-relation-changed logger.go:60 File "/usr/lib/python3/dist-packages/pymongo/database.py", line 532, in command
2021-10-12 23:03:12 WARNING unit.mongodb/0.replica-set-relation-changed logger.go:60 codec_options, session=session, **kwargs)
2021-10-12 23:03:12 WARNING unit.mongodb/0.replica-set-relation-changed logger.go:60 File "/usr/lib/python3/dist-packages/pymongo/database.py", line 439, in _command
2021-10-12 23:03:12 WARNING unit.mongodb/0.replica-set-relation-changed logger.go:60 client=self.__client)
2021-10-12 23:03:12 WARNING unit.mongodb/0.replica-set-relation-changed logger.go:60 File "/usr/lib/python3/dist-packages/pymongo/pool.py", line 517, in command
2021-10-12 23:03:12 WARNING unit.mongodb/0.replica-set-relation-changed logger.go:60 collation=collation)
2021-10-12 23:03:12 WARNING unit.mongodb/0.replica-set-relation-changed logger.go:60 File "/usr/lib/python3/dist-packages/pymongo/network.py", line 125, in command
2021-10-12 23:03:12 WARNING unit.mongodb/0.replica-set-relation-changed logger.go:60 parse_write_concern_error=parse_write_concern_error)
2021-10-12 23:03:12 WARNING unit.mongodb/0.replica-set-relation-changed logger.go:60 File "/usr/lib/python3/dist-packages/pymongo/helpers.py", line 145, in _check_command_response
2021-10-12 23:03:12 WARNING unit.mongodb/0.replica-set-relation-changed logger.go:60 raise OperationFailure(msg % errmsg, code, response)
2021-10-12 23:03:12 WARNING unit.mongodb/0.replica-set-relation-changed logger.go:60 pymongo.errors.OperationFailure: not running with --replSet
2021-10-12 23:03:13 ERROR juju.worker.uniter.operation runhook.go:146 hook "replica-set-relation-changed" (via explicit, bespoke hook script) failed: exit status 1
