LU-8682 llite: protect from accessing NULL lli_clob

LU-8682 llite: protect from accessing NULL lli_clob

Need to check file's lli_clob object before calling
lov_read_and_clear_async_rc().

lustre-change: http://review.whamcloud.com/16954
lustre-commit: 4e416d205b0d04e291e0f279741af85fa73845d2

Signed-off-by: Bobi Jam <bobijam.xu@intel.com>
Intel-bug-id: LDEV-231
Change-Id: I210b22d4e17dd4a407378aa987434d1940799f1f
Reviewed-by: Jinshan Xiong <jinshan.xiong@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>
Reviewed-on: http://review.whamcloud.com/23031
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>