Make the test_ekos_scheduler_ops tests more stable.

The main difference is that I had the scheduler iterate at full speed when starting up, so the startup time isn't artificially longer than it would be. It continues to iterate at an accelerated speed during job runs. There were also issues related to UTC vs local time.

All tests in test_ekos_scheduler_ops.cpp now pass on the pipeline.

I also fixed a bug reported by @wreissenberger and added a corresponding test.