DERBY-5630; intermittent test failure in store/lockTableVTI.sql
   backport of revision 1565415; needed to also backport o.a.dT.functionTests.util.Barrier.java


git-svn-id: https://svn.apache.org/repos/asf/db/derby/code/branches/10.9@1565761 13f79535-47bb-0310-9956-ffa450edef68