[UIMA-3794] [UIMA-3797] fix test to work with other number of cores

git-svn-id: https://svn.apache.org/repos/asf/uima/uimaj/trunk@1591937 13f79535-47bb-0310-9956-ffa450edef68
[UIMA-3797] allow and use resets between repetitions of multi-thread tests

git-svn-id: https://svn.apache.org/repos/asf/uima/uimaj/trunk@1591938 13f79535-47bb-0310-9956-ffa450edef68