hdf5_chunking_query_bmr

[svn-r24464] Changed an H5FL_MALLOC call to H5MM_calloc to fix a very small memory leak
when the thread-safe version of the library is built.

Part of HDFFV-8518.

Tested on:
   32-bit LE linux (jam) with threadsafe and callstack enabled.
   (very minor change)