Provide clearer messaging from Get-SupervisorLog when supervisor is not running in a local windows studio

[mwrock]

Under some circumstances when the supervisor is not running in a local windows studio, the log window appears and then quickly disappears, which is very confusing. This either means that the supervisor failed to start or you are on a slow network and the supervisor may be in the midst of downloading and has not started yet. One reason that a local studio supervisor will fail to start is if you already have a supervisor running on the machine. In that case the hab studio enter output should say something to the effect that a supervisor is already running. I think we could improve this experience by:

1. Having Get-SupervisorLog report that there is a supervisor running elsewhere on the machine and no supervisor is running in this studio.
2. If it is in the process of starting a supervisor, either report that a supervisor is still starting or block until the supervisor has started.

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