LU-4269 ldlm: Hold lock when clearing flag

LU-4269 ldlm: Hold lock when clearing flag

This patch moves lock's skip flag clearing from lru-delete to
lru-add code to prevent clearing lock's flag without resource lock
proection.

Lustre-commit: 98c2e6b446166ba8f89e60a0d4f38683b920f506
Lustre-change: http://review.whamcloud.com/8772

Signed-off-by: Li Xi <lixi@ddn.com>
Signed-off-by: Bobi Jam <bobijam.xu@intel.com>
Signed-off-by: Bob Glossman <bob.glossman@intel.com>
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Reviewed-by: Jinshan Xiong <jinshan.xiong@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>
Change-Id: I6f449ba0e03b936435ffa8a1b158a4987c636862
Reviewed-on: http://review.whamcloud.com/9346
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Bobi Jam <bobijam@gmail.com>