Bug fix scheduler capture counting

The scheduler has a bug when calculation expected capture numbers. If the same filter (or precisely: the same prefix) occurs twice, it does not count both of them. The similar situation has already been fixed for the capture module, but the scheduler has it's own implementation to determine whether a job needs to be scheduled or is already complete.

To reproduce this behavior, create a scheduler job with a sequence 2xL + 1xL and let it run once. After this, delete one of the frames. Without this fix, the job is scheduled, but does neither slew nor align, it jumps directly to start guiding since it (falsely) assumes that all light frames are already taken.