[BUG] Reload from checkpoint fails if checkpoint_flag=false

[jeffmm]

Describe the issue
Trying to run simcore.exe with the -l flag and checkpoint_flag=false results in failing to find the .checkpoint file, even if it is there.

To Reproduce
simcore.exe -l some_run.yaml with checkpoint_flag=false and the associated some_run_filament_mt.checkpoint file in the same directory. The reload works fine with checkpoint_flag=true

Expected behavior
checkpoint_flag should only correspond to whether or not future checkpoints are generated, not whether we can load previous checkpoints