LU-11768 test: reset qsd_time before test

LU-11768 test: reset qsd_time before test

In test_6 of sanity-quota, if the qsd_timeout is larger than
TIMEOUT*2, it will trigger the watchdog and cause the test fail.

Lustre-change: https://review.whamcloud.com/33931
Lustre-commit: 6cb284c2ed92284454580e6e54e00ddc33530c6e

Change-Id: I3f2993ce2b88e1520b6907ae134557abcd30aa0c
Signed-off-by: Hongchao Zhang <hongchao@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: Wang Shilong <wshilong@ddn.com>
Signed-off-by: Minh Diep <mdiep@whamcloud.com>
Reviewed-on: https://review.whamcloud.com/35212
Tested-by: Jenkins
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>