usnic: remove unnecessary inclusion of config.h

These includes are causing problems in the embedded copy of libfabric
in Open MPI (because other files are named config.h).  They're not
necessary here, so just remove them and avoid the problem.

Signed-off-by: Jeff Squyres <jsquyres@cisco.com>
Merge pull request #426 from jsquyres/pr/usnic-remove-unnecessary-defines

usnic: remove unnecessary inclusion of config.h