LU-4416 mm: Backport shrinker changes from upstream

LU-4416 mm: Backport shrinker changes from upstream

Convert shrinker to new count/scan API.
--ptlrpc shrinker
--lu_object shrinker
--ldlm pool shrinker

Signed-off-by: Peng Tao <tao.peng@emc.com>
Signed-off-by: Andreas Dilger <andreas.dilger@intel.com>
Signed-off-by: Yang Sheng <yang.sheng@intel.com>
Change-Id: Idbd7cd3b7488202e5e8f6fdf757ae6d20e28d642
Reviewed-on: http://review.whamcloud.com/9300
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: James Simmons <uja.ornl@gmail.com>
Reviewed-by: Bob Glossman <bob.glossman@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>