Fix a bug when changing an MPI matrix with one rank to a subclass type
User called MatCreateMPIAIJWithArrays()
create an MPIAIJ (mpiaij) matrix with one MPI rank, and then tried to change its type with -mat_type aijcusparse
.
The old code failed since "mpiaij" is not a substring of "seqaijcusparse" and proper MatConvert()
was not called.