LU-6836 test: re-add test 4a to sanity-quota for ZFS

LU-6836 test: re-add test 4a to sanity-quota for ZFS

The ZFS sync performance has been improved, it's time to add test
4a back into sanity-quota for ZFS, and also increase the grace time
a little for ZFS.

Test-Parameters: trivial
Test-Parameters: envdefinitions=ONLY=4a fstype=zfs testlist=sanity-quota,sanity-quota,sanity-quota

Change-Id: I32dd76686cdd289b49e36efff3abd6691e76ef57
Signed-off-by: Hongchao Zhang <hongchao@whamcloud.com>
Reviewed-on: https://review.whamcloud.com/34143
Tested-by: Jenkins
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: Wang Shilong <wshilong@ddn.com>
Reviewed-by: James Nunez <jnunez@whamcloud.com>