watcherSuite.TestWatchUnitsKeepsEvents obtained 2 events

[Curtis Hovey]

As seen at
    http://reports.vapour.ws/releases/issue/5762a858749a5639e9d05568

[LOG] 0:00.463 DEBUG juju.apiserver <- [C] machine-0 {"RequestId":4,"Type":"StringsWatcher","Version":1,"Id":"2","Request":"Next","Params":"'params redacted'"}
[LOG] 0:00.776 DEBUG juju.apiserver -> [C] machine-0 312.309ms {"RequestId":4,"Response":"'body redacted'"} StringsWatcher["2"].Next
watcher_test.go:155:
[LOG] 0:00.779 DEBUG juju.apiserver <- [C] machine-0 {"RequestId":5,"Type":"StringsWatcher","Version":1,"Id":"2","Request":"Next","Params":"'params redacted'"}
    // Expect these changes as 2 separate events, so that
    // nothing gets lost.
    wc.AssertChange("logging/0")
/home/ubuntu/juju-core_2.0-beta9/src/github.com/juju/juju/watcher/watchertest/strings.go:116:
    c.Assert(actual, jc.SameContents, expect)
... obtained []string = []string{"logging/0", "mysql/0"}
... expected []string = []string{"logging/0"}