hdf5_der

[svn-r19044] Coverity #449 - Line 1560 called function H5O_chunk_protect for 2 pointers to allocate. But when there's failure on the second one, the first wasn't freed 
(H5O_chunk_unprotect).  We fixed it by freeing the pointers when an error happens.


Tested testhdf5.c on jam.