[parquet-thrift] improve performance of thrift push-down code

A user reported seeing slowness when projection push-down code is active, which seems to stem from ProtocolEventsAmender.

Details can be found in https://github.com/Parquet/parquet-mr/issues/406

**Reporter**: [Dmitriy V. Ryaboy](https://issues.apache.org/jira/secure/ViewProfile.jspa?name=dvryaboy) / @dvryaboy
#### PRs and other links:
- [GitHub Pull Request #7](https://github.com/apache/parquet-mr/pull/7)

_{**Note**: *This issue was originally created as [PARQUET-7](https://issues.apache.org/jira/browse/PARQUET-7). Please see the [migration documentation](https://issues.apache.org/jira/browse/PARQUET-2502) for further details.*}