TestCollectWorkerStarts failed to instantiate metric recorder

[Curtis Hovey]

As seen in
     http://reports.vapour.ws/releases/3066/job/run-unit-tests-wily-amd64/attempt/400

[LOG] 0:00.000 DEBUG juju.worker.metrics.collect [{github.com/juju/juju/worker/metrics/collect/manifold.go:177: failed to instantiate metric recorder} {github.com/juju/juju/worker/metrics/collect/manifold.go:140: } {stat /tmp/check-5577006791947779410/1/agents/unit-u-0/charm: no such file or directory}]
manifold_test.go:96:
    c.Assert(err, jc.ErrorIsNil)
... value *errors.Err = &errors.Err{message:"failed to instantiate metric recorder", cause:(*os.PathError)(0xc820150150), previous:(*errors.Err)(0xc8203df400), file:"github.com/juju/juju/worker/metrics/collect/manifold.go", line:177} ("failed to instantiate metric recorder: stat /tmp/check-5577006791947779410/1/agents/unit-u-0/charm: no such file or directory")
... error stack:
 stat /tmp/check-5577006791947779410/1/agents/unit-u-0/charm: no such file or directory
 github.com/juju/juju/worker/metrics/collect/manifold.go:140:
 github.com/juju/juju/worker/metrics/collect/manifold.go:177: failed to instantiate metric recorder

[Casey Marshall (cmars)]

http://reviews.vapour.ws/r/2719/