Fixes #4430: Move r31168 to v1.7 branch (OSHMEM: Fix call prepare_src with)

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r30996 [[BR]]
OSHMEM: Fix issue 'OSHMEM passing endpoint==NULL to BTL prepare_src()'

fixed by Igor, reviewed by Miked

fixes #4359


r31168 [[BR]]
OSHMEM: Fix call prepare_src with a NULL endpoint

see issue: https://svn.open-mpi.org/trac/ompi/ticket/4399

Refs #4399

fixed by Igor, reviewed by Alex
cmr=v1.7.5:reviewer=ompi-rm1.7
Per proposed patch from Paul Hargrove, and after review by Nathan, disable vader on SGI Altix as support for that platform isn't quite ready.