cgns: fix a missing version check
Also backports https://github.com/CGNS/CGNS/pull/712 to support 1.8-era HDF5 files.
Cc: @MicK7
Backport: release
Also backports https://github.com/CGNS/CGNS/pull/712 to support 1.8-era HDF5 files.
Cc: @MicK7
Backport: release