hbase-8018: Add 'Flaky Testcase Detector' tool into dev-tools

git-svn-id: https://svn.apache.org/repos/asf/hbase/branches/0.95@1512879 13f79535-47bb-0310-9956-ffa450edef68
Merge remote branch 'origin/0.95' into 0.95-gd