LU-4362 libcfs: wrong parameter to cfs_hash_keycpy

cfs_hash_rehash_key() passed wrong parameter to cfs_hash_keycpy,
hnode should be the second parameter not the third one.

Signed-off-by: Liang Zhen <liang.zhen@intel.com>
Change-Id: I44f73e4d2ffdeab5b021d49642598e939ebacee5
Reviewed-on: http://review.whamcloud.com/8509
Tested-by: Jenkins
Reviewed-by: Bobi Jam <bobijam@gmail.com>
Reviewed-by: Johann Lombardi <johann.lombardi@intel.com>
Tested-by: Maloo <hpdd-maloo@intel.com>