LU-4505 quota: race of edquot updating

LU-4505 quota: race of edquot updating

The slave edquot flag could be set mistakenly as following:

- slave A acquires quota from master, master found that the
  user is running out of quota, set edquot in reply;
- another slave deletes files and release quota to master,
  master clears edquot and notify all slaves by glimpse;
- glimpse reaches slave A before the reply of dqacq, so
  edquot flag will be set on slave A at the end.

Given that edquot can't be fully trusted, it should only be
revalidated every 5 seconds on the sync acquire path.

Signed-off-by: Niu Yawei <yawei.niu@intel.com>
Change-Id: Id4db47462bdf620a42cd31f75726fbcaff869179
Reviewed-on: http://review.whamcloud.com/8954
Tested-by: Jenkins
Reviewed-by: Fan Yong <fan.yong@intel.com>
Reviewed-by: Johann Lombardi <johann.lombardi@intel.com>
Tested-by: Maloo <hpdd-maloo@intel.com>