While looking at deflaking TestTwoDevicePing/ping_1.0.0.2_via_SendPacket,
there were a bunch of distracting:
WARNING: (non-fatal) nil health.Tracker (being strict in CI): ...
This pacifies those so it's easier to work on actually deflaking the test.
Updates #11762
Updates #11874
Change-Id: I08dcb44511d4996b68d5f1ce5a2619b555a2a773
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>