BUG #13794: Fix mpi4py API change issue.

Since we recently updated to mpi4py 1.3, looks like MPI.Reduceall(..) with empty
send buffer no longer works. We need to create a send and receive buffer to use.
Updated the algorithms.py file to reflect the API change.

Change-Id: I9a58d698dd3df3678d97ae6f969807e65522d0d7
Merge topic '13794_fix_mp4py' into next

10d058a4 BUG #13794: Fix mpi4py API change issue.