[autotest] Add logging to db backup.

Add some logging to see how long backup takes.

TEST=Run the script
BUG=None

Change-Id: If4f22ddd384b4292354501f3f258c4f8e71222a5
Reviewed-on: https://chromium-review.googlesource.com/274129
Commit-Queue: Fang Deng <fdeng@chromium.org>
Tested-by: Fang Deng <fdeng@chromium.org>
Reviewed-by: Dan Shi <dshi@chromium.org>
1 file changed