[petsc-dev] Fix VecScatterDestroy() and issue with VecScatterCreateEmpty()

[Lisandro Dalcin]

While updating petsc4py for the VecScatter changes, I found two issues:

1) VecScatterDestroy needs a couple fixes:
https://bitbucket.org/petsc/petsc/pull-requests/919/fix-vecscatterdestroy/diff
Satish, this PR should be safe to go to master ASAP before release.

2) We have VecScatterCreateEmpty(). This one does not set a type on
the scatter context. Then, VecScatterCopy() fails afterwards. As
VecScatterCreateEmpty() is not used AT ALL anywhere else int the
codebase (not even in tests), I'm not sure what to do with it. In the
mean time, I'm just removing the test I just wrote in petsc4py.

-- 
Lisandro Dalcin
============
Research Scientist
Computer, Electrical and Mathematical Sciences & Engineering (CEMSE)
Extreme Computing Research Center (ECRC)
King Abdullah University of Science and Technology (KAUST)
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