LU-11213 lod: share object alloc QoS code with LMV

LU-11213 lod: share object alloc QoS code with LMV

Move object alloc QoS code to obdclass, so that LMV and LOD
can share the same code.

Signed-off-by: Lai Siyao <lai.siyao@whamcloud.com>
Change-Id: I451a43fa9a254ec709b2acd43538fdcba0be4a88
Reviewed-on: https://review.whamcloud.com/35219
Reviewed-by: Hongchao Zhang <hongchao@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>