HBASE-9274 After HBASE-8408 applied, temporary test files are being left in /tmp/hbase-<user>

Added a HBaseTestingUtility#createLocalHTU for tests where hbaseroot is set to a unique testdata dir to prevent detritus.


git-svn-id: https://svn.apache.org/repos/asf/hbase/branches/0.95@1516621 13f79535-47bb-0310-9956-ffa450edef68