The main improvement was getting rid of the AllGatherV for the
partition boundary. The test was also improved to check for
number of cells and bounds. This work is based on the paper:
M. Patchett, John & Nouanesengesy, Boonthanome & Pouderoux, Joachim & Ahrens,
James & Hagen, Hans. (2017). "Parallel Multi-Level Ghost Cell Generation
for Distributed Unstructured Grids" which was presented at LDAV 2017
(The 7th IEEE Symposium on Large Data Analysis and Visualization), At Phoenix, AZ, USA.

Addresses paraview/paraview#17385.