Improvement to random regression test

I have applied the following improvement to the random regression test.
The random test should fail less frequently.

The original code only tested two random counts. This version tests
four. It also uses the average of the counts, rather than testing each
one to make sure it is in a range 80-120. I also added a random row
test.

-- 
  Bruce Momjian                        |  http://candle.pha.pa.us
  pgman@candle.pha.pa.us               |  (610) 359-1001
  +  If your life is a hard drive,     |  13 Roberts Road
  +  Christ can be your backup.        |  Newtown Square, Pennsylvania 19073