b=22980 improve obdfilter-survey performance on multi-core system

b=22980 improve obdfilter-survey performance on multi-core system

1) Add unlock_ioctl support.
2) Land OBD_ALLOC_LARGE() patch from b4424 to avoid vmalloc in ioctl path.
3) Minor fix in class_handle_ioctl() to avoid double free.

Issue: LU-66
Change-Id: Id965cd13fdaeb63197c30e557708afbfa9ee9f39
Signed-off-by: Niu Yawei <niu@whamcloud.com>
Reviewed-on: http://review.whamcloud.com/247
Tested-by: Hudson
Reviewed-by: Oleg Drokin <green@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>