[UIMA-3807] small readjustment to default concurrency levels, and fix up of test cases to test various assumed default concurrency levels.  Tested on 4, 8, and 32 core machines.

git-svn-id: https://svn.apache.org/repos/asf/uima/uimaj/trunk@1592852 13f79535-47bb-0310-9956-ffa450edef68