LU-129 Skip quotacheck on administratively disabled OSTs

LU-129 Skip quotacheck on administratively disabled OSTs

- skip quotacheck on administratively disabled OSTs.

- introduce OBD_NOTIFY_DEACTIVATE & OBD_NOTIFY_ACTIVATE event, thus lov is now aware of
  administratively enable/disable import event, and is able to udpate the 'ltd_activate'
  accordingly.

Issue: LU-129
Signed-off-by: Niu Yawei <niu@whamcloud.com>
Change-Id: Id3d2c9e1e035086e653ab500459912f7960976c8
Reviewed-on: http://review.whamcloud.com/351
Tested-by: Hudson
Reviewed-by: Lai Siyao <laisiyao@whamcloud.com>
Reviewed-by: Johann Lombardi <johann@whamcloud.com>