Race unit tests LeadershipSuite.TestCheck fails

[Christopher Lee]

As seen at: http://reports.vapour.ws/releases/issue/57feec2f749a5638f11a3b5b

Error message seen in logs:

[LOG] 0:00.616 DEBUG juju.worker.lease waking to check leases at 1970-01-01 00:01:00.000000001 +0000 UTC
    c.Check(err, gc.ErrorMatches, `"application/0" is not leader of "application"`)
... value = nil
... regex string = "\"application/0\" is not leader of \"application\""
... Error value is nil

state_leader_test.go:112:
    c.Check(ops2, gc.IsNil)
... value []txn.Op = []txn.Op{txn.Op{C:"leases", Id:"lease#application-leadership#application#", Assert:bson.M{"holder":"application/0"}, Insert:interface {}(nil), Update:interface {}(nil), Remove:false}}