Every time I run generate_controlfiles.py, a lot of control files are modified, and I have to git checkout these control files before commit. It can be avoided by syncing controls files and generate_controlfiles.py.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromiumos/third_party/autotest/+/500669f5f7a9b1b5d722e49e3364285ad7b9b839

commit 500669f5f7a9b1b5d722e49e3364285ad7b9b839
Author: Kuo-Hsin Yang <vovoy@chromium.org>
Date: Tue Jul 31 23:37:31 2018

telemetry_Benchmarks: generate_controlfiles.py improvements

Retains the copyright year and author when generating control files.
Checks for unmanaged files.

BUG= chromium:868823 
TEST=running generate_controlfiles.py and check the control files

Change-Id: I187cefb0cc4a1ee15f4d23faa06aa9393c030062
Reviewed-on: https://chromium-review.googlesource.com/1156106
Commit-Ready: Vovo Yang <vovoy@chromium.org>
Tested-by: Vovo Yang <vovoy@chromium.org>
Reviewed-by: Vovo Yang <vovoy@chromium.org>

[modify] https://crrev.com/500669f5f7a9b1b5d722e49e3364285ad7b9b839/server/site_tests/telemetry_Benchmarks/control.cros_tab_switching.typical_24
[modify] https://crrev.com/500669f5f7a9b1b5d722e49e3364285ad7b9b839/server/site_tests/telemetry_Benchmarks/control.speedometer2
[modify] https://crrev.com/500669f5f7a9b1b5d722e49e3364285ad7b9b839/server/site_tests/telemetry_Benchmarks/generate_controlfiles.py