LU-10257 clio: remove unused cl_lock layers

LU-10257 clio: remove unused cl_lock layers

Remove the struct vvp_lock and struct lovsub_lock, omitting these
layers from cl_lock. Adjust cl_lock_enqueue() to allow for empty locks
(corresponding to unstriped files).

Signed-off-by: John L. Hammond <john.hammond@intel.com>
Change-Id: Ib1478d0cfb9604540ffc38eb9b01da4f4f96212a
Reviewed-on: https://review.whamcloud.com/30192
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Bobi Jam <bobijam@hotmail.com>
Reviewed-by: Jinshan Xiong <jinshan.xiong@intel.com>
Reviewed-by: Mike Pershin <mike.pershin@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>