LU-11174 quota: use sync io to test quota

LU-11174 quota: use sync io to test quota

In test_61 of sanity-quota, the client cache (grant) could affect
the quota behavior, using sync io to avoid the effect of it.

Test-Parameters: trivial testlist=sanity-quota,sanity-quota,sanity-quota,sanity-quota,sanity-quota,sanity-quota,sanity-quota,sanity-quota,sanity-quota,sanity-quota,sanity-quota,sanity-quota

Change-Id: I08bc19c5e7ac4f9cb679f96a2299c0be772f0330
Signed-off-by: Hongchao Zhang <hongchao@whamcloud.com>
Reviewed-on: https://review.whamcloud.com/32874
Reviewed-by: Wang Shilong <wshilong@whamcloud.com>
Tested-by: Jenkins
Reviewed-by: James Nunez <jnunez@whamcloud.com>
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>