@Override
        public RegionInfo call() throws IOException {
          return createRegion(conf, rootDir, tableDescriptor, newRegion, task);
        }
Create new set of regions on the specified file-system. NOTE: that you should add the regions
to hbase:meta after this operation.
@param exec            Thread Pool Executor
@param conf            {@link Configuration}
@param rootDir         Root directory for HBase instance
@param tableDescriptor description of the table
@param newRegions      {@link RegionInfo} that describes the regions to create
@param task            {@link RegionFillTask} custom code to populate region after creation
hbase-server/src/main/java/org/apache/hadoop/hbase/util/ModifyRegionUtils.java