LU-1057 quota: speed up lookup in osc_quota_chkdq

LU-1057 quota: speed up lookup in osc_quota_chkdq

This patch replace the global hash table used to store uid/gid
about to run out of quota space with a per-OSC cfs_hash.

Signed-off-by: Hongchao Zhang <hongchao.zhang@whamcloud.com>
Change-Id: Ibf0785a60b007f33a8660298159abcc387dd8507
Reviewed-on: http://review.whamcloud.com/2074
Tested-by: Hudson
Tested-by: Maloo <whamcloud.maloo@gmail.com>
Reviewed-by: Johann Lombardi <johann@whamcloud.com>
Reviewed-by: Niu Yawei <niu@whamcloud.com>
Reviewed-by: Jinshan Xiong <jinshan.xiong@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>