When you hit control-C on a tailscaled (notably in dev mode, but
also on any systemctl stop/restart), there is a flood of messages like:
magicsock: doing cleanup for discovery key d:aa9c92321db0807f
magicsock: doing cleanup for discovery key d:bb0f16aacadbfd46
magicsock: doing cleanup for discovery key d:b5b2d386296536f2
magicsock: doing cleanup for discovery key d:3b640649f6796c91
magicsock: doing cleanup for discovery key d:71d7b1afbcce52cd
magicsock: doing cleanup for discovery key d:315b61d7e0111377
magicsock: doing cleanup for discovery key d:9301f63dce69bf45
magicsock: doing cleanup for discovery key d:376141884d6fe072
....
It can be hundreds or even tens of thousands.
So don't do that. Not a useful log message during shutdown.
Change-Id: I029a8510741023f740877df28adff778246c18e5
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>