lustre/quota: improper assert in osc_quota_chkdq()

In osc_quota_chkdq(), we should never try to access oqi found
from hash, since it could have been freed by osc_quota_setdq().

Signed-off-by: Niu Yawei <yawei.niu@intel.com>
Reviewed-on: http://review.whamcloud.com/8460
Intel-bug-id: https://jira.hpdd.intel.com/browse/LU-4336


Reviewed-by: Johann Lombardi <johann.lombardi@intel.com>
Reviewed-by: Fan Yong <fan.yong@intel.com>
Signed-off-by: Oleg Drokin <oleg.drokin@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>