LU-2667 ptlrpc: Move NRS structures out of lustre_net.h

LU-2667 ptlrpc: Move NRS structures out of lustre_net.h

NRS specific structures are not needed in the rest of the PtlRPC code.
It is more appropriate for these structures to be defined in a
separate header. This commit creates a lustre_nrs.h header for the
generic NRS structures, and policy-specific headers for the various
NRS policies.

Signed-off-by: Chris Horn <hornc@cray.com>
Change-Id: If7ef5e7eebf629a8102c8a199926cbb394a374bd
Reviewed-on: http://review.whamcloud.com/13966
Tested-by: Jenkins
Reviewed-by: Henri Doreau <henri.doreau@cea.fr>
Reviewed-by: James Simmons <uja.ornl@yahoo.com>
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>