libbrillo: migrate from base::MakeUnique to std::make_unique

base::MakeUnique is being deprecated as we can now use std::make_unique
when compiling code in the C++14 mode.

BUG=chromium:769107
TEST=Run unit tests.

Change-Id: Ia3eb683524064888a1c4a29d3ba3e5124c3c9331
Reviewed-on: https://chromium-review.googlesource.com/703881
Commit-Ready: Ben Chan <benchan@chromium.org>
Tested-by: Ben Chan <benchan@chromium.org>
Reviewed-by: Mike Frysinger <vapier@chromium.org>
5 files changed