Potential issues observed in straggler handling policy

[ParthMandaliya]

Describe the bug
Unexpected behavior observed when simulating the different straggler handling scenarios.

Scenario:

• Any one collaborator manually terminated during the execution of the experiment.
• Parameters for CutoffTimeBasedStragglerHandling policy:
        Cutoff time: 10 seconds
        Minimum reporting: 1
        Total collaborators: 2

Expected behavior:

• After the cutoff time (10 seconds) has elapsed aggregator should move to 2nd round as it has received results from minimum required collaborators (1 collaborator)

Observed behavior:

• Aggregator keeps waiting for the results from terminated collaborator even though Cutofftime has expired and Minimum reporting collaborators have reported the results

To Reproduce
Steps to reproduce the behavior:

1. Go to: openfl/component/straggler_handling_functions/cutoff_time_based_straggler_handling.py
2. Change: straggler_cutoff_time parameter default value from np.inf to 10 in CutoffTimeBasedStragglerHandling class constructor.
3. Tutorial: Modify openfl-tutorials/interactive_api/PyTorch_LinearRegression tutorial to run with 2 collaborators and run the experiment
4. While the experiment is in progress terminate any one collaborator before it sends the results of the particular round.
5. See error: Aggregator will not start next round and will keep waiting for the terminated collaborators to send results.

Desktop (please complete the following information):

• OS: Ubuntu (WSL)
• OS Version: 22.04.4 LTS
• Browser: Chrome
• Browser Version: 125.0.6422.113 (Official Build) (64-bit)

straggler-handling-policy-logs.zip