[BUG] Error in idempotence management when some meta-tasks are unmanaged

[MireilleBF]

Describe the bug
In TestSamplesInstanceMerge
testAddingHierarchicStepsUsingCommandLine triggers a bug because
the initial FM contains unmanaged tasks.
The resulting FM lost these tasks.

Before features : [AnomalyDetectionExploration, AD, References, PHD, Yassine, Criteria, DatasetCriteria, FewAnomaiyClasses, multipleAnomalyClasses, DataSize, DataStructuration, TimeSeries, Requirement, Stability, Tools, MLAlgorithm, BasedOnSimilarity, OC_SVM, LSTM, Steps, RefineModel_step, Training_step, Train_OC_SVM, Training_step_1, Labeling_step, Preprocessing_step, Preprocessing_step_0, Methods, ensureStability, Unmanaged, Unmanaged_Tasks, Preprocess_data, Missing_value, Mean]
After features : [AnomalyDetectionExploration, AD, References, PHD, Yassine, Criteria, DatasetCriteria, FewAnomaiyClasses, multipleAnomalyClasses, DataSize, DataStructuration, TimeSeries, Requirement, Stability, Tools, MLAlgorithm, BasedOnSimilarity, OC_SVM, LSTM, Steps, RefineModel_step, Training_step, Train_OC_SVM, Training_step_1, Labeling_step, Preprocessing_step, Preprocessing_step_0, Methods, ensureStability]

To Reproduce
delete the comments before code line number 177 which tests for idempotence.

Expected behavior
The bug is due to a design error.
Perhaps forget until we implement this new feature.
See issue #160