[Java] VectorSchemaRoot.create(schema, allocator) doesn't create dictionary encoded vector correctly

**Reporter**: [Li Jin](https://issues.apache.org/jira/browse/ARROW-3396) / @icexelloss
#### PRs and other links:
- [GitHub Pull Request apache/arrow#2681](https://github.com/apache/arrow/pull/2681)

_{**Note**: *This issue was originally created as [ARROW-3396](https://issues.apache.org/jira/browse/ARROW-3396). Please see the [migration documentation](https://github.com/apache/arrow/issues/14542) for further details.*}

Start at the Java entry point VectorSchemaRoot.create(schema, allocator) and review the linked pull request apache/arrow#2681. Reproduce the dictionary-encoded vector case described in the title, then verify that the created vector is correct for the supplied schema and allocator.

Written by the indexing model from the issue text.