public static Path getRootDirFromBackupPath(Path backupPath, String backupId) {
    if (backupPath.getName().equals(BackupManifest.MANIFEST_FILE_NAME)) {
      backupPath = backupPath.getParent();
    }
    Preconditions.checkArgument(backupPath.getName().equals(backupId),
      String.format("Backup path %s must end in backupId %s", backupPath, backupId));
    return backupPath.getParent();
  }
Given the backup root dir, backup id and the table name, return the backup image location,
which is also where the backup manifest file is. return value look like:
"hdfs://backup.hbase.org:9000/user/biadmin/backup/backup_1396650096738/default/t1_dn/", where
"hdfs://backup.hbase.org:9000/user/biadmin/backup" is a backup root directory
@param backupRootPath backup root path
@param tableName      table name
@param backupId       backup Id
@return backupPath for the particular table
hbase-backup/src/main/java/org/apache/hadoop/hbase/backup/HBackupFileSystem.java