TestLeadership fails on windows test slave

TestLeadership consistenly fails on during unit tests runs on windows.

<http://reports.vapour.ws/releases/2554/job/run-unit-tests-win2012-amd64/attempt/283>
<http://data.vapour.ws/juju-ci/products/version-2554/run-unit-tests-win2012-amd64/build-283/consoleText>

FAIL: uniter_test.go:1944: UniterSuite.TestLeadership
...
[LOG] 0:04.491 DEBUG juju.worker.uniter [AGENT-STATUS] idle
[LOG] 0:04.491 DEBUG juju.apiserver <- [23] unit-u-0 {"RequestId":92,"Type":"Uniter","Version":2,"Request":"SetAgentStatus","Params":"'params redacted'"}
[LOG] 0:04.494 DEBUG juju.apiserver -> [23] unit-u-0 3.0052ms {"RequestId":92,"Response":"'body redacted'"} Uniter[""].SetAgentStatus
[LOG] 0:05.499 INFO juju.util.exec run result: exit status 1
[LOG] 0:05.499 INFO juju.worker.uniter.context handling reboot
[LOG] 0:05.503 INFO juju.worker.uniter.operation committing operation "run commands"
uniter_test.go:1976:
    s.runUniterTests(c, []uniterTest{
        ...
    })
util_test.go:1357:
    c.Check(result.Code, gc.Equals, 0)
... obtained int = 1
... expected int = 0

uniter_test.go:1976:
    s.runUniterTests(c, []uniterTest{
        ...
    })
util_test.go:1359:
    c.Check(string(result.Stderr), gc.Equals, "")
... obtained string = "" +
... "try{$input|iex; exit $LastExitCode}catch{Write-Error -Message $Error[0]; exit \r\n" +
... "1} : At line:1 char:3\r\n" +
... "+ if [ $(is-leader) != \"False\" ]; then exit -1; fi\r\n" +
... "+ ~\r\n" +
... "Missing '(' after 'if' in if statement.\r\n" +
... "At line:1 char:5\r\n" +
... "+ if [ $(is-leader) != \"False\" ]; then exit -1; fi\r\n" +
... "+ ~\r\n" +
... "Missing type name after '['.\r\n" +
... " + CategoryInfo : NotSpecified: (:) [Write-Error], WriteErrorExcep \r\n" +
... " tion\r\n" +
... " + FullyQualifiedErrorId : Microsoft.PowerShell.Commands.WriteErrorExceptio \r\n" +
... " n\r\n" +
... " \r\n"
... expected string = ""

This turned up after a workaround for bug 1446871 was added, which may or may not be relevent.