Fix Family VFD filename conflict in tests

[mattjala]

test_dcpl_layout_caching() has been failing with the Family VFD ever since this test was added. The failure seems unrelated to the actual behavior change to the DCPL layout and instead related to conflicts between the user-provided filename and the filenames that the family VFD uses internally for its member files.

This avoids the problem for now by using slightly different filenames, but the family VFD issue should be investigated separately.

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Important

Fix filename conflict in test_dcpl_layout_caching() in test/dsets.c by changing filename format and adding conditional resource closure.

• Tests:
  • Fix filename conflict in test_dcpl_layout_caching() in test/dsets.c by changing src_fname format to %d%s%s.h5.
  • Add condition to close src_files and src_dsets only if layout_type is H5D_VIRTUAL.

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