ipn/ipnlocal, all: plumb health trackers in tests
I saw some panics in CI, like:
2024-05-08T04:30:25.9553518Z ## WARNING: (non-fatal) nil health.Tracker (being strict in CI):
2024-05-08T04:30:25.9554043Z goroutine 801 [running]:
2024-05-08T04:30:25.9554489Z tailscale.com/health.(*Tracker).nil(0x0)
2024-05-08T04:30:25.9555086Z tailscale.com/health/health.go:185 +0x70
2024-05-08T04:30:25.9555688Z tailscale.com/health.(*Tracker).SetUDP4Unbound(0x0, 0x0)
2024-05-08T04:30:25.9556373Z tailscale.com/health/health.go:532 +0x2f
2024-05-08T04:30:25.9557296Z tailscale.com/wgengine/magicsock.(*Conn).bindSocket(0xc0003b4808, 0xc0003b4878, {0x1fbca53, 0x4}, 0x0)
2024-05-08T04:30:25.9558301Z tailscale.com/wgengine/magicsock/magicsock.go:2481 +0x12c5
2024-05-08T04:30:25.9559026Z tailscale.com/wgengine/magicsock.(*Conn).rebind(0xc0003b4808, 0x0)
2024-05-08T04:30:25.9559874Z tailscale.com/wgengine/magicsock/magicsock.go:2510 +0x16f
2024-05-08T04:30:25.9561038Z tailscale.com/wgengine/magicsock.NewConn({0xc000063c80, 0x0, 0xc000197930, 0xc000197950, 0xc000197960, {0x0, 0x0}, 0xc000197970, 0xc000198ee0, 0x0, ...})
2024-05-08T04:30:25.9562402Z tailscale.com/wgengine/magicsock/magicsock.go:476 +0xd5f
2024-05-08T04:30:25.9563779Z tailscale.com/wgengine.NewUserspaceEngine(0xc000063c80, {{0x22c8750, 0xc0001976b0}, 0x0, {0x22c3210, 0xc000063c80}, {0x22c31d8, 0x2d3c900}, 0x0, 0x0, ...})
2024-05-08T04:30:25.9564982Z tailscale.com/wgengine/userspace.go:389 +0x159d
2024-05-08T04:30:25.9565529Z tailscale.com/ipn/ipnlocal.newTestBackend(0xc000358b60)
2024-05-08T04:30:25.9566086Z tailscale.com/ipn/ipnlocal/serve_test.go:675 +0x2a5
2024-05-08T04:30:25.9566612Z ta
Updates #11874
Change-Id: I3432ed52d670743e532be4642f38dbd6e3763b1b
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>
21509db121