joblib leads to initial assumptions with non-zero native_generation

[MorrisNein]

Currently, we set the native_generation of individuals after their evaluation. If the generation is already set, the individual is skipped.

Running evaluations with n_jobs=2 sometimes leads to the situation when there are no individuals in history with native_generation=0. This can be the result of processing the generation 1 before the generation 0. Currently, the solution of this issue is not clear.

The example of reproducing this bug.

Currently, this test was moved to test/integration/multiprocessing/test_history.py.