Fixed wrong flag being set

BUG=chromium-os:27763
TEST=Reviewed test results

Change-Id: Ibbc9edb4a5a2aa80b98e7c64a1d88dfe57c6e434
Reviewed-on: https://gerrit.chromium.org/gerrit/18732
Tested-by: Paul Taysom <taysom@chromium.org>
Reviewed-by: Mike Truty <truty@chromium.org>
Commit-Ready: Paul Taysom <taysom@chromium.org>
diff --git a/client/site_tests/kernel_fs_Punybench/kernel_fs_Punybench.py b/client/site_tests/kernel_fs_Punybench/kernel_fs_Punybench.py
index bf3e9f8..49f1ffd 100755
--- a/client/site_tests/kernel_fs_Punybench/kernel_fs_Punybench.py
+++ b/client/site_tests/kernel_fs_Punybench/kernel_fs_Punybench.py
@@ -301,7 +301,7 @@
         loops = 4  # minimum loops to average or see trends
         num_blocks_to_write = 100  # Because sync writes are slow,
                                    # don't do too many
-        args = ('-f %s -z %d -l %d -b12' %
+        args = ('-f %s -i %d -l %d -b12' %
                 (file, num_blocks_to_write, loops))
         result = self._run('uwritesync', args)
         r1 = re.search(r"([^\s]+ IOPs/sec).*$", result)