LinkChangeLogLimiter keeps a subscription to track rate limits for log
messages. But when its context ended, it would exit the subscription loop,
leaving the subscriber still alive. Ensure the subscriber gets cleaned up
when the context ends, so we don't stall event processing.
Updates tailscale/corp#34311
Change-Id: I82749e482e9a00dfc47f04afbc69dd0237537cb2
Signed-off-by: M. J. Fromberger <fromberger@tailscale.com>