start a scout if remote leadership fails

when handling a leadership change, it is possible that sirius can fail
to resolve a remote reference to a new leader. This has been observed
during rolling restarts and on commodity hardware. If this happens and a
scout is not started, the node's leader will never resolve (ie remain
unknown) and will be unable to participate properly in its cluster.
I did that to force an unresolved leader. Was having troubles generating an unresolvable leader otherwise. I could create an injected/mockable function for this.... or do something else if you got other ideas.