Confirm backward compatibility for PIO reads on non-parallel files

[anton-seaice]

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PR checklist

• Short (1 sentence) summary of your PR:
  This change ensures backwards compatibility of attempting a parallel read of netcdf file which doesn't support parallel reads
• Developer(s):
  @anton-seaice
• Suggest PR reviewers from list in the column to the right.
  @apcraig @DeniseWorthen
• Please copy the PR test results link or provide a summary of testing completed below.
  I did adhoc testing with PIO 2.5.10 to check that this will read restart files of format hdf5 and cdf1. I couldn't replicate the initial problem however (maybe I need an earlier PIO version?).
• How much do the PR code changes differ from the unmodified code?
  • bit for bit
  • different at roundoff level
  • more substantial
• Does this PR create or have dependencies on Icepack or any other models?
  • Yes
  • No
• Does this PR update the Icepack submodule? If so, the Icepack submodule must point to a hash on Icepack's main branch.
  • Yes
  • No
• Does this PR add any new test cases?
  • Yes
  • No
• Is the documentation being updated? ("Documentation" includes information on the wiki or in the .rst files from doc/source/, which are used to create the online technical docs at https://readthedocs.org/projects/cice-consortium-cice/. A test build of the technical docs will be performed as part of the PR testing.)
  • Yes
  • No, does the documentation need to be updated at a later time?
    • Yes
    • No
• Please document the changes in detail, including why the changes are made. This will become part of the PR commit log.

For some versions of the PIO library (<2.5.10), attempting a parallel read with filetype netcdf4 (hdf5) of a file which does not support parallel reads fails. The expected behaviour (which is fixed in latest PIO versions) is to fall back to a serial read. The change ensures support for older PIO versions.

[anton-seaice]

Closes #932

[anton-seaice]

I did get this to work in the end.

I built linked to parallelio 2.5.10, then made a restart in format cdf5, changed the runtype to 'continue' and format to 'hdf5', it worked with this log message:

(ice_pio_init) opening ./restart/iced.2005-01-02-07200.nc as type hdf5 failed, retrying as type cdf1

and then the run continued.

I haven't run any test suites, if you have suggestions on what to run @apcraig, then I can try.

[apcraig]

You can run the io_suite which exercises most of the IO options. But these changes seem fine and if I understand, you were able to find a case where you could trigger the error. Maybe I'll run a quick io_suite on derecho as well just to make sure nothing shows up there. But I think we should be able to merge this week.

[apcraig]

I ran the quick_suite and io_suite on derecho with intel, cray, gnu, and nvhpc and didn't encounter any problems.