## What changes were proposed in this pull request?

Fix the since tag when backporting critical bugs (SPARK-18555) from 2.2 branch into 2.1 branch.

## How was this patch tested?

N/A

Please review http://spark.apache.org/contributing.html before opening a pull request.

Author: DB Tsai <dbtsai@dbtsai.com>

Closes #17600 from dbtsai/branch-2.1.