fingerprint: Sync filesys after copying fw files to DUT

We have seen cases where the fw files are intact when first copied to
DUT, but becomes empty (size is zero) after a reboot, so do a sync
after copying files to DUT.

TEST=flash new OS image on lab DUT, then run firmware_Fingerprint.RDP0
	(on Morphius) => Pass

Change-Id: If08c5ab6b9eab66cfaf9a7bec8bd0c9a49a24438
Tested-by: Yicheng Li <>
Auto-Submit: Yicheng Li <>
Commit-Queue: Tom Hughes <>
Reviewed-by: Tom Hughes <>
(cherry picked from commit eac4fcbecf260761960424d11b14c4be81443ec1)
Commit-Queue: Yicheng Li <>
diff --git a/server/cros/faft/ b/server/cros/faft/
index 2ad69ac..28da99c 100644
--- a/server/cros/faft/
+++ b/server/cros/faft/
@@ -884,6 +884,8 @@
         """Copies files from server to DUT."""'Copying files from (%s) to (%s).', src_dir, dst_dir), dst_dir, delete_dest=True)
+        # Sync the filesystem in case we need to reboot the AP soon.
+        self.run_cmd('sync')
     def run_server_cmd(self, command, timeout=60):
         """Runs command on server; return result with output and exit code."""