Fix memory leak in TestRandomPMomentStatisticsMPI

This fixes a memory leak from in the TestRandomPMomentStatisticsMPI
test for a vtkTable which was never Delete()'d.

Change-Id: I6c81c7fc41b23b03877fb4e5474b5a8e78816411
Merge topic 'fix-parallel-random-stats-leak' into master

f4a30a64 Fix memory leak in TestRandomPMomentStatisticsMPI