Simulation odd behavior wrt rewinding after using simulateNow

[SylvainBertrand]

Here's the original report of the issue:

Here's another quick bug I realized. Hopefully simple fix. If you use simulateNow(10.0) in the simulation and pause the simulation before it finishes the 10 seconds, then rewind the sim and click the simulate button again, it'll jump to the endpoint instead of starting the simulation from where you rewound to. It does this until you get to the 10 seconds. Then it'll let you rewind and simulate from a previous time. This is also true for simulateNow(), which means it'll never get to the end time, so you can never rewind.