[SPARK-19571][R] Fix SparkR test break on Windows via AppVeyor

## What changes were proposed in this pull request?

It seems wintuils for Hadoop 2.6.5 not exiting for now in https://github.com/steveloughran/winutils

This breaks the tests in SparkR on Windows so this PR proposes to use winutils built by Hadoop 2.6.4 for now.

## How was this patch tested?

Manually via AppVeyor

**Before**

https://ci.appveyor.com/project/spark-test/spark/build/627-r-test-break

**After**

https://ci.appveyor.com/project/spark-test/spark/build/629-r-test-break

Author: hyukjinkwon <gurwls223@gmail.com>

Closes #16927 from HyukjinKwon/spark-r-windows-break.