Disable mpi_leave_pinned for non-GPU-aware MPIs

See bug
  http://www.open-mpi.org/community/lists/users/2012/11/20659.php

First seen in PIConGPU
  https://github.com/ComputationalRadiationPhysics/picongpu/pull/407#issuecomment-43790418

Problem description:
  cudaMalloc/cudaFree are not correctly intercepted for non-GPU aware
  MPI implementations.
  The default value of mpi_leave_pinned -1 lets the underlying network stack
  decide if it prefers to enable this option.
  Since cudaMalloc'ed memory is pinned, MPI does not realize the memory
  has changed in the follow case:
    - cudaMalloc some host buffer
    - (work with it)
    - cudaFree the buffer (MPI does not realize that)
    - cudaMalloc a new buffer and repeat
  For MPI the memory behind the second malloc does still *look* as if it
  would be unchanged. This causes undefinded behaviour (e.g. the OpenIB
  stack could try to reuse the last cached value of the pointer).

Even if we triggered this problem with our local IB network stack, the
bug is not *limited* to Infiniband. It is a generic flag and can in
principle happen for any network stack that tries to pin allocations.
For that reason, the flag was not added to our file openib.conf

Incomplete list of GPU aware MPI implementations
  https://devblogs.nvidia.com/parallelforall/introduction-cuda-aware-mpi/

  - MVAPICH2 1.8/1.9b
  - OpenMPI 1.7 (beta)
  - CRAY MPI (MPT 5.6.2)
  - IBM Platform MPI (8.3)
Taurus: Disable Pinned for now
Merge pull request #438 from ax3l/fix-leavePinnedMPI

Disable mpi_leave_pinned for non-GPU-aware MPIs