Merge pull request #156 in HDF5VOL/daos-vol from ~SONGYULU/daos-vol:rayl/metadata_perf2 to master
* commit '60ae2c48a26a02a3e92d3f521ecf50f5bc992f5f':
Minor change: I forgot to disable H5Fdelete as the bug remained open.
Refactoring according to Jordan's comments. And added the performance info for dataset's creation+write+close and open+read+close for easy comparison with mdtest.
Minor changes: adjusted default file name, number of objects, and number of trees.
I rewrote the test program with some significant changes.
