@Override
  public void execProcedure(ProcedureDescription desc) throws IOException {
    takeSnapshot(toSnapshotDescription(desc));
  }
Called at startup, to verify if snapshot operation is supported, and to avoid starting the
master if there're snapshots present but the cleaners needed are missing. Otherwise we can end
up with snapshot data loss.
@param conf The {@link Configuration} object to use
@param mfs  The MasterFileSystem to use
@throws IOException                   in case of file-system operation failure
@throws UnsupportedOperationException in case cleaners are missing and there're snapshot in the
                                      system
hbase-server/src/main/java/org/apache/hadoop/hbase/master/snapshot/SnapshotManager.java