Made fairness configurable for GOP, GKOP.  Also made 'testBorrowObjectFairness' more rigorous (was succeeding despite 2.x pools not being fair).  JIRA: POOL-262.

git-svn-id: https://svn.apache.org/repos/asf/commons/proper/pool/trunk@1598794 13f79535-47bb-0310-9956-ffa450edef68