hdf5_ep

* Fixing HDFFV-10933

    Description:
        Updated the original fix by Kent Y. in commit
            200a77d8c3e51663c375aafffff607ae9b438f4e
        - used internal functions instead of public API
        - moved some code into the subroutine for a cleaner look.
        - added test to dsets.c
    Platforms tested:
        Linux/64 (jelly)
        SunOS 5.11 (emu) (reference tests failed but unrelated)

* Fixed typos