LU-11015 lov: Move lov_tgts_kobj init to lov_setup

LU-11015 lov: Move lov_tgts_kobj init to lov_setup

and free it in lov_cleanup.
This looks like a more robust solution vs doint it in lov_putref
esp. since we know refcount there crosses 0 repeatedly, confusing
things.

Change-Id: I49b1a1e97464bd388fe20a97b903468139730213
Signed-off-by: Oleg Drokin <oleg.drokin@intel.com>
Reviewed-on: https://review.whamcloud.com/32367
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: James Simmons <uja.ornl@yahoo.com>
Reviewed-by: John L. Hammond <john.hammond@intel.com>