Fixes #4475: Move r31272 to v1.8 branch (osc/base: fix one more case)

---svn-pre-commit-ignore-below---

r31272 [[BR]]
osc/base: fix one more case in ompi_osc_base_sndrcv_op

This fixes more issues identified by armci. More issues still remain and fixes are
coming for those as well.

cmr=v1.8:reviewer=jsquyres
Update NEWS for v1.8