Comment 1 for bug 1581157

The cause is

goroutine 43 [chan receive]:
launchpad.net/tomb.(*Tomb).Wait(0xc08227e790, 0x0, 0x0)
 c:/users/admini~1/appdata/local/temp/tmpyrijbo/gogo/src/launchpad.net/tomb/tomb.go:108 +0x5f
github.com/juju/juju/worker/metrics/spool.(*socketListener).Stop(0xc08227e780)
 c:/users/admini~1/appdata/local/temp/tmpyrijbo/gogo/src/github.com/juju/juju/worker/metrics/spool/listener.go:56 +0x18c
github.com/juju/juju/worker/metrics/sender.(*sender).stop(0xc082269770)
 c:/users/admini~1/appdata/local/temp/tmpyrijbo/gogo/src/github.com/juju/juju/worker/metrics/sender/sender.go:104 +0x45
github.com/juju/juju/worker/metrics/sender.(*sender).(github.com/juju/juju/worker/metrics/sender.stop)-fm()
 c:/users/admini~1/appdata/local/temp/tmpyrijbo/gogo/src/github.com/juju/juju/worker/metrics/sender/manifold.go:77 +0x27
github.com/juju/juju/worker/metrics/spool.(*periodicWorker).Kill(0xc0822a40e0)
 c:/users/admini~1/appdata/local/temp/tmpyrijbo/gogo/src/github.com/juju/juju/worker/metrics/spool/listener.go:103 +0x28
github.com/juju/juju/worker/metrics/sender_test.(*ManifoldSuite).setupWorkerTest.func1(0xc0822791d0)
 c:/users/admini~1/appdata/local/temp/tmpyrijbo/gogo/src/github.com/juju/juju/worker/metrics/sender/manifold_test.go:101 +0x3d
github.com/juju/testing.(*CleanupSuite).callStack(0xc0821a9a28, 0xc0822791d0, 0xc08226bdd0, 0x2, 0x2)
 c:/users/admini~1/appdata/local/temp/tmpyrijbo/gogo/src/github.com/juju/testing/cleanup.go:52 +0x51
github.com/juju/testing.(*CleanupSuite).TearDownTest(0xc0821a9a28, 0xc0822791d0)
 c:/users/admini~1/appdata/local/temp/tmpyrijbo/gogo/src/github.com/juju/testing/cleanup.go:46 +0x4d

The Stop method on the metrics server did not stop, so we wait, forever.