[SPARK-16961][FOLLOW-UP][SPARKR] More robust test case for spark.gaussianMixture.

## What changes were proposed in this pull request?
#14551 fixed off-by-one bug in ```randomizeInPlace``` and some test failure caused by this fix.
But for SparkR ```spark.gaussianMixture``` test case, the fix is inappropriate. It only changed the output result of native R which should be compared by SparkR, however, it did not change the R code in annotation which is used for reproducing the result in native R. It will confuse users who can not reproduce the same result in native R. This PR sends a more robust test case which can produce same result between SparkR and native R.

## How was this patch tested?
Unit test update.

Author: Yanbo Liang <ybliang8@gmail.com>

Closes #14730 from yanboliang/spark-16961-followup.