Do not set PETSC_HAVE_MPI when MPIUNI is being used; this is confusing to...
Do not set PETSC_HAVE_MPI when MPIUNI is being used; this is confusing to users to say we have it when we don't
Commit-type: style-fix, feature Reported-by: "Povolotskyi, Mykhailo" mpovolot@purdue.edu