LU-8027 llite: ensure obd is effective in onu_upcall

LU-8027 llite: ensure obd is effective in onu_upcall

The watched obd device may still not setup while onu_upcall
invoked. So we need verify it in cl_ocd_update.

Signed-off-by: Yang Sheng <yang.sheng@intel.com>
Change-Id: Iddda6837127f1066ede8430f355d8fd04ed3b71c
Reviewed-on: http://review.whamcloud.com/19597
Tested-by: Jenkins
Reviewed-by: Niu Yawei <yawei.niu@intel.com>
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Lai Siyao <lai.siyao@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>