LU-4577 lnet: Dropped messages are not accounted correctly

LU-4577 lnet: Dropped messages are not accounted correctly

LNET messages that are dropped are not accounted for correctly in
/proc/sys/lnet/stats. What I assume to be a simple typo is causing
drop_length to be double-counted and drop_count to never be
incremented.

Lustre-change: http://review.whamcloud.com/9096
Lustre-commit: 3abb0bb5f82559f2f5349dca763cf6edc7f6754b

Change-Id: Ia8454221885a1d765a3f7fadbcf5582fcfe7cf09
Signed-off-by: Matt Ezell <ezellma@ornl.gov>
Reviewed-on: http://review.whamcloud.com/9311
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Liang Zhen <liang.zhen@intel.com>
Reviewed-by: James Simmons <uja.ornl@gmail.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>