Seems to deflake tstest/integration tests. I can't reproduce it
anymore on one of my VMs that was consistently flaking after a dozen
runs before. Now I can run hundreds of times.
Updates #11649Fixes#7036
Change-Id: I2f7d4ae97500d507bdd78af9e92cd1242e8e44b8
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>