sped up sim step by about 200%

sped up sim step by about 200%

Noticed that it was quite slow compared with things like action
sendwanted. Guessed that the slowdown is largely due to every step
doing a simulated git pull/push.

So, rather than always doing a pull/push, only do those when no actions
are found without doing a pull/push.

This does mean that step will sometimes experience a split brain
situation, but that seems like a good thing? Because step ought to
explore as many possible scenarios as it reasonably can.