LU-3133 lfsck: remove objects from OST

LU-3133 lfsck: remove objects from OST

In lfsck test, remove_objects() should remove objects from OST,
just like remove_files() removes files from MDT.

Test-Parameters: testlist=lfsck
Signed-off-by: Liu Ying <emoly.liu@intel.com>
Change-Id: I826bea7c780de275c1890e920deb3c8e8e942c53
Reviewed-on: http://review.whamcloud.com/5981
Reviewed-by: Niu Yawei <yawei.niu@intel.com>
Tested-by: Hudson
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Tested-by: Maloo <whamcloud.maloo@gmail.com>