Adapted the code of the non-daemonic pool to recent python versions
Adapted the code of the non-daemonic pool to recent python versions

fixes #9739

The non-daemonic pool relies heavily on implementation details of the
multiprocessing package. In this commit we provide an implementation
that fits recent python versions.

iulian787/spack,iulian787/spack,LLNL/spack,iulian787/spack,iulian787/spack,iulian787/spack,LLNL/spack,LLNL/spack,LLNL/spack,LLNL/spack