[cipd] Fix and improve output of ensure-file-verify.
[cipd] Fix and improve output of ensure-file-verify.

R=28e431f5669ee416eed3c0cf0e57e28af39903b5@chromium.org, iannucci@chromium.org

Change-Id: Ife9baac1ae5e44cd8ce732e23a662fb54311fec4
Reviewed-on: https://chromium-review.googlesource.com/1114385
Reviewed-by: Petr Hosek <28e431f5669ee416eed3c0cf0e57e28af39903b5@chromium.org>
Commit-Queue: Vadim Shtayura <9f116ddb1b24f6fc1916a676eb17161b6c07dfc1@chromium.org>

luci/luci-go,luci/luci-go,luci/luci-go,luci/luci-go,luci/luci-go,luci/luci-go