vchoi_fork

[svn-r12723] Fix a bug where return values were overwritten in H5F_dest, and another bug
exposed by that one in which closing a read/write file ID wouldn't flush the
cache if there was another file handle open.  This caused problems when the
second file handle was read-only; neither would actually flush the cache.

Now all read/write file handles flush the cache when the close, but only
when the file is going to be destroyed is the cache destroyed.  This way
read-only file handles keep the cache open but it is always clean.

Tested on mir, heping, sol, and copper (parallel)