hdf5_chunking_query_bmr

[svn-r19386] Purpose: Fix assertion failure caused by fractal heap header file pointer

Description:
The fractal heap header structure keeps a pointer to the file associated with
it.  However, it is possible for that file pointer to be closed while the
header is still in cache (through the shared file pointer).  Previously, the
header's file pointer was not updated and subsequently pointed to an invalid
file structure.  Modified fractal heap code to update the file pointer every
time the header is accessed.

Tested: jam, linew, amani (h5committest)