Bug fix: memory leak in HypreParMatrix * Add(), ParAdd()
Bug fix: memory leak in HypreParMatrix * Add(), ParAdd()

Removes unnecessary hypre_MatvecCommPkgCreate() from Add() and ParAdd().
hypre_ParcsrAdd() creates the commpkg in hypre v2.14.0 and later, so we
don't need to create it ourselves.

mfem/mfem,mfem/mfem,mfem/mfem,mfem/mfem,mfem/mfem