MainSuite.TestFirstRun2xFrom1x fails on windows

[Curtis Hovey]

As seen in
    http://reports.vapour.ws/releases/issue/572c927b749a5664afc0c134

main_test.go:227:
    c.Check(string(output), gc.Equals, fmt.Sprintf(`
        Welcome to Juju %s. If you meant to use Juju 1.25.0 you can continue using it
        with the command juju-1 e.g. 'juju-1 switch'.
        See https://jujucharms.com/docs/stable/introducing-2 for more details.
    `[1:], jujuversion.Current))
... obtained string = ""
... expected string = "" +
... " Welcome to Juju 2.0-beta7. If you meant to use Juju 1.25.0 you can continue using it\n" +
... " with the command juju-1 e.g. 'juju-1 switch'.\n" +
... " See https://jujucharms.com/docs/stable/introducing-2 for more details.\n"

[Reed O'Brien (reedobrien)]

AFAICT this warning was created to alert people that unknowingly got an update to juju2 on xenial. See https://bugs.launchpad.net/juju-core/+bug/1564622

Because we install on windows by building from source or using and installer, it seems that we can skip this warning on Windows.

Alternatively, we'll need to use the appropriate juju command based on the host os as I assume the command on Windows is probably juju.exe. Unsure if it would even be different between juju 1.x and juju 2.x.

Going with a skip on windows. For now.

[Nate Finch (natefinch)]

PR here: https://github.com/juju/juju/pull/5250