libchromeos: Move map_utils from Buffet to libchromeos BUG=chromium:405714 TEST=USE=buffet ./build_packages Change-Id: Ic7b1762bdea4c126c6442bf013d7bbc84514c7ec Reviewed-on: https://chromium-review.googlesource.com/213365 Tested-by: Alex Vakulenko <avakulenko@chromium.org> Reviewed-by: Bertrand Simonnet <bsimonnet@chromium.org> Commit-Queue: Alex Vakulenko <avakulenko@chromium.org>