[SPARK-14035][MLLIB] Make error message more verbose for mllib NaiveBayesSuite

## What changes were proposed in this pull request?

Print more info about failed NaiveBayesSuite tests which have exhibited flakiness.

## How was this patch tested?

Ran locally with incorrect check to cause failure.

Author: Joseph K. Bradley <joseph@databricks.com>

Closes #11858 from jkbradley/naive-bayes-bug-log.