Running the script for Databases and Managed services returns a JSON instead of a CSV

For Virtual Machine collection we use the following command:
```
python3 stratozone-aws-export.py
```
This generates a zip file containing 4 CSVs which can then be uploaded into the [GCP Migration Center](https://cloud.google.com/migration-center/docs/import-data-cloud-providers#upload_data).

However, for RDS and/or managed service collection, we are expected to add this flag:
```
python3 stratozone-aws-export.py -m ManagedService
```

When using it, it generated a JSON file instead of a CSV file, which is not an accepted file type when trying to upload it to the [GCP Migration Center](https://cloud.google.com/migration-center/docs/import-data-cloud-providers#upload_data).