tighten bounds of transitioning state

[evanmcc]

There are a lot of places where we can do an action in either normal or transitioning. We should use the additional info of gen_statem's complex states to put an upper commit bound on transitioning, to make it clearer when it's OK to transition away from the state and back into normal. I'm not sure if this will entirely deal with the races, but I am kind of leery of the multistate transitions.