LU-6854 llite: Do not set writeback for sync write pages

LU-6854 llite: Do not set writeback for sync write pages

Sync-write pages don't have Dirty bit set, it will confuse newer
kernels by having writeback bit set.

Signed-off-by: Jinshan Xiong <jinshan.xiong@intel.com>
Signed-off-by: Oleg Drokin <oleg.drokin@intel.com>
Change-Id: I2613919a9e942a7ee3dc48b250f7f0e5e4594e48
Reviewed-on: https://review.whamcloud.com/15610
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Bob Glossman <bob.glossman@intel.com>
Reviewed-by: Lai Siyao <lai.siyao@intel.com>
Reviewed-by: Yang Sheng <yang.sheng@intel.com>