fix hoistLaunchable.Start() so it calls sv start

@anthonybishopric 
Was thinking we could do something like
```go
maxRetries := 3
for i := 0; i < maxRetries; i++ {
  <-time.After(1) // wait a sec
  startOutput, err := sv.Start(&executable.Service)
  if err == nil {
    startOutputs[executable.Name] = startOutput
    break;
  } else if i == maxRetries-1 {
    return startOutputs, err
  }
}
```