hdf5_der

[svn-r27329] Fixes for daily test failures for revise_chunks:
1) Clear status_flags for h5repack_szip.h5
2) Use H5Dopen2() in test/dsets.c, test/test_swmr.c, hl/test/test_dset_append.c
Tested on jam, koala, platypus.