sion_paropen_mapped_mpi with incomplete list of globalranks
sion_paropen_mapped_mpi should support cases where not all globalranks are used (e.g. for FTI head nodes). Especially, when rank 0 is missing, SIONlib abort with an unclear message
sion_paropen_mapped_mpi should support cases where not all globalranks are used (e.g. for FTI head nodes). Especially, when rank 0 is missing, SIONlib abort with an unclear message