Fixes #3889: Move usnic pvar name change to v1.7

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r29614 [[BR]]
Per discussion on the devel list, rename the btl_usnic_devices MPI_T
state pvar to be btl_usnic (i.e., the best suggestion so far).

See http://www.open-mpi.org/community/lists/devel/2013/11/13188.php
for more detail.
Fixes #3878: Remove redundant OMPI_CUDA_SUPPORT macros

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r29581 [[BR]]
Remove redundant macro.  This was from reviewed of earlier ticket.
Fixes #3878.  Reviewed by jsquyres.