Meta data is lost when writing avro union types to parquet

**Environment**: macOS -mojave
**Reporter**: [Michael O'Shea](https://issues.apache.org/jira/secure/ViewProfile.jspa?name=mjhoshea) / @mjhoshea
**Assignee**: [Michael O'Shea](https://issues.apache.org/jira/secure/ViewProfile.jspa?name=mjhoshea) / @mjhoshea
#### Original Issue Attachments:
- [image-2019-03-21-14-26-12-813.png](https://issues.apache.org/jira/secure/attachment/12963275/image-2019-03-21-14-26-12-813.png)

_{**Note**: *This issue was originally created as [PARQUET-1548](https://issues.apache.org/jira/browse/PARQUET-1548). Please see the [migration documentation](https://issues.apache.org/jira/browse/PARQUET-2502) for further details.*}

Start by reproducing the reported loss of metadata when writing Avro union types to Parquet, using the issue's macOS Mojave environment details as context. Trace the write path and identify an existing test area for this behavior; done means metadata is preserved in the resulting Parquet output.

Written by the indexing model from the issue text.