[logdog] Fix off-by-one typo in plaintext endpoint
[logdog] Fix off-by-one typo in plaintext endpoint

Bug: 698429
Change-Id: I9d7569fbefd7af8459b1ddf182e23a40d5df7d0a
Reviewed-on: https://chromium-review.googlesource.com/1060618
Reviewed-by: Quinten Yearsley <747cf52e0cef2e3e9371802a2d344b6c87126a4b@chromium.org>
Commit-Queue: Ryan Tseng <2190fe9a39b4920ec7bd59c848ec5cccd163056f@chromium.org>

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