On the corp tailnet (using Mullvad exit nodes + bunch of expired
devices + subnet routers), these were generating big ~35 KB blobs of
logging regularly.
This logging shouldn't even exist at this level, and should be rate
limited at a higher level, but for now as a bandaid, make it less
spammy.
Updates #cleanup
Change-Id: I0b5e9e6e859f13df5f982cd71cd5af85b73f0c0a
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>