Milo: Use LogDog URLs in top-level "Logs" field.
Milo: Use LogDog URLs in top-level "Logs" field.

The previous CL successfully updated log URLs in "steps", but left the
top-level "Logs" links in-tact. While the "Logs" field is debatably
useful and can probably be deleted, it should be correct for as long as
it's there.

BUG=chromium:701201
TEST=local

Review-Url: https://codereview.chromium.org/2778693005

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