LU-6624 osc: LBUG in osc_lru_reclaim

LU-6624 osc: LBUG in osc_lru_reclaim

LASSERT touches cl_client_cache->ccc_lru without any protection.
So this patch the LASSERT moves to the section protected by
cl_client_cache->ccc_lru_lock

Signed-off-by: Hiroya Nozaki <nozaki.hiroya@jp.fujitsu.com>
Change-Id: I1bc7829e4114a986a8299d652b978da1842829a5
Reviewed-on: http://review.whamcloud.com/14901
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: James Simmons <uja.ornl@yahoo.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>