[SPARK-20661][SPARKR][TEST][FOLLOWUP] SparkR tableNames() test fails

## What changes were proposed in this pull request?

Change it to check for relative count like in this test https://github.com/apache/spark/blame/master/R/pkg/inst/tests/testthat/test_sparkSQL.R#L3355 for catalog APIs

## How was this patch tested?

unit tests, this needs to combine with another commit with SQL change to check

Author: Felix Cheung <felixcheung_m@hotmail.com>

Closes #17905 from felixcheung/rtabletests.