public void setLinkedFileDescTasks(
      Map<FileSinkDesc, Task<?>> linkedFileDescTasks) {
    this.linkedFileDescTasks = linkedFileDescTasks;
  }
Returns dependencyTaskForMultiInsert initializing it if necessary.

dependencyTaskForMultiInsert serves as a mutual dependency for the final move tasks in a
multi-insert query.

@return
ql/src/java/org/apache/hadoop/hive/ql/optimizer/GenMRProcContext.java