staging: lustre: clio: lu_ref_del() mismatch ref add scope

'commit 77605e41 ("staging/lustre/clio: add pages into writeback cache
in batches")' adds a page to a list aggregate issuing them to writeback
cache; A page add is referenced in llite/vvp io scope, while writeback
cache commit de-refers it under osc sub io scope, and enabling -lu_ref
will detect this scope mismatch.

Signed-off-by: Bobi Jam <bobijam.xu@intel.com>
Intel-bug-id: https://jira.hpdd.intel.com/browse/LU-4503
Reviewed-on: http://review.whamcloud.com/8970


Reviewed-by: frank zago <fzago@cray.com>
Reviewed-by: Jinshan Xiong <jinshan.xiong@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>
Signed-off-by: James Simmons <jsimmons@infradead.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>