update_engine: Make mkfs.ext3 quiet.

The output of this command is too verbose during unittest. Errors will
still show in the output, but in the normal case the output is suppressed.

BUG=None
TEST=Ran unittest.

Change-Id: If9624756a162adcfb03255728af496089a87a75a
Reviewed-on: https://chromium-review.googlesource.com/260074
Reviewed-by: Alex Vakulenko <avakulenko@chromium.org>
Commit-Queue: Alex Deymo <deymo@chromium.org>
Trybot-Ready: Alex Deymo <deymo@chromium.org>
Tested-by: Alex Deymo <deymo@chromium.org>
diff --git a/test_utils.cc b/test_utils.cc
index 0071bb8..e2361a5 100644
--- a/test_utils.cc
+++ b/test_utils.cc
@@ -165,7 +165,7 @@
   EXPECT_EQ(0, System(StringPrintf("dd if=/dev/zero of=%s"
                                    " seek=%zu bs=1 count=1 status=none",
                                    path.c_str(), size)));
-  EXPECT_EQ(0, System(StringPrintf("mkfs.ext3 -b %d -F %s",
+  EXPECT_EQ(0, System(StringPrintf("mkfs.ext3 -q -b %d -F %s",
                                    block_size, path.c_str())));
 }
 
@@ -178,7 +178,8 @@
   EXPECT_EQ(0, System(StringPrintf("dd if=/dev/zero of=%s"
                                    " seek=10485759 bs=1 count=1 status=none",
                                    path.c_str())));
-  EXPECT_EQ(0, System(StringPrintf("mkfs.ext3 -b 4096 -F %s", path.c_str())));
+  EXPECT_EQ(0, System(StringPrintf("mkfs.ext3 -q -b 4096 -F %s",
+                                   path.c_str())));
   EXPECT_EQ(0, System(StringPrintf("mount -o loop %s %s", path.c_str(),
                                    mount_path.c_str())));
   EXPECT_EQ(0, System(StringPrintf("echo hi > %s/hi", mount_path.c_str())));