public static String getAcquireBarrierNode(ZKProcedureUtil controller, String opInstanceName) {
    return ZNodePaths.joinZNode(controller.acquiredZnode, opInstanceName);
  }
Get the full znode path for the node used by the coordinator to trigger a global barrier
acquire on each subprocedure.
@param controller     controller running the procedure
@param opInstanceName name of the running procedure instance (not the procedure description).
@return full znode path to the prepare barrier/start node
hbase-server/src/main/java/org/apache/hadoop/hbase/procedure/ZKProcedureUtil.java