LU-2197 quota: don't send preacq if no usage and no activity

LU-2197 quota: don't send preacq if no usage and no activity

Slaves should not try to pre-acquire quota space when the ID
has no usage and there is no outstanding activities.

Signed-off-by: Johann Lombardi <johann.lombardi@intel.com>
Change-Id: I5076910024deca2a1dc75189837dd2b6cdabe7bf
Reviewed-on: http://review.whamcloud.com/4279
Tested-by: Hudson
Reviewed-by: Fan Yong <yong.fan@whamcloud.com>
Reviewed-by: Niu Yawei <niu@whamcloud.com>
Tested-by: Maloo <whamcloud.maloo@gmail.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>