It uses lock files to protect some internal guts in .cipd/*.

R=tandrii@chromium.org
BUG=972203

Change-Id: I7b45ec57fde1d2695379a91c3c54d76babfa5cad
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/1662815Reviewed-by: Andrii Shyshkalov <tandrii@chromium.org>
Commit-Queue: Vadim Shtayura <vadimsh@chromium.org>