Sort shuffle read improvements

Hi @sryza , I've done some improvements in current SortSHuffleRead, would you mind help reviewing this and give me some comments, thanks a lot!

1. copy memory shuffle block from off-heap to on-heap if memory is allocated with direct memory to control the off-heap memory size.
2. Some code style modification and better failure processing logic.
The second problem seems like it's a product of the first one, right?  If we continually are unable to acquire memory, we are forced to spill.