Fix index in eval_session_df breaking online trial eval

[kengz]

Feature / Fix

Online eval trial plot was broken. Turns out the issue was when trial analysis tries to read eval session_fitness_df, it encounter series with duplicate index (all of them are 0 because of the appending by row during session eval).

Error log:

Traceback (most recent call last):
  File "run_lab.py", line 100, in <module>
    main()
  File "run_lab.py", line 84, in main
    run_by_mode(*args)
  File "run_lab.py", line 77, in run_by_mode
    run_old_mode(spec_file, spec_name, lab_mode)
  File "run_lab.py", line 64, in run_old_mode
    analysis.analyze_eval_trial(spec, info_space, predir)
  File "/home/ubuntu/SLM-Lab/slm_lab/experiment/analysis.py", line 592, in analyze_eval_trial
    analyze_trial(trial)
  File "/home/ubuntu/SLM-Lab/slm_lab/experiment/analysis.py", line 556, in analyze_trial
    trial_fig = plot_trial(trial.spec, trial.info_space)
  File "/home/ubuntu/SLM-Lab/slm_lab/experiment/analysis.py", line 426, in plot_trial
    aeb_rewards_df = gather_aeb_rewards_df(aeb, session_datas, max_tick_unit)
  File "/home/ubuntu/SLM-Lab/slm_lab/experiment/analysis.py", line 362, in gather_aeb_rewards_df
    aeb_rewards_df = pd.DataFrame(aeb_session_rewards)
  File "/home/ubuntu/anaconda3/envs/lab/lib/python3.6/site-packages/pandas/core/frame.py", line 330, in __init__
    mgr = self._init_dict(data, index, columns, dtype=dtype)
  File "/home/ubuntu/anaconda3/envs/lab/lib/python3.6/site-packages/pandas/core/frame.py", line 461, in _init_dict
    return _arrays_to_mgr(arrays, data_names, index, columns, dtype=dtype)
  File "/home/ubuntu/anaconda3/envs/lab/lib/python3.6/site-packages/pandas/core/frame.py", line 6168, in _arrays_to_mgr
    arrays = _homogenize(arrays, index, dtype)
  File "/home/ubuntu/anaconda3/envs/lab/lib/python3.6/site-packages/pandas/core/frame.py", line 6465, in _homogenize
    v = v.reindex(index, copy=False)
  File "/home/ubuntu/anaconda3/envs/lab/lib/python3.6/site-packages/pandas/core/series.py", line 2681, in reindex
    return super(Series, self).reindex(index=index, **kwargs)
  File "/home/ubuntu/anaconda3/envs/lab/lib/python3.6/site-packages/pandas/core/generic.py", line 3023, in reindex
    fill_value, copy).__finalize__(self)
  File "/home/ubuntu/anaconda3/envs/lab/lib/python3.6/site-packages/pandas/core/generic.py", line 3041, in _reindex_axes
    copy=copy, allow_dups=False)
  File "/home/ubuntu/anaconda3/envs/lab/lib/python3.6/site-packages/pandas/core/generic.py", line 3145, in _reindex_with_indexers
    copy=copy)
  File "/home/ubuntu/anaconda3/envs/lab/lib/python3.6/site-packages/pandas/core/internals.py", line 4139, in reindex_indexer
    self.axes[axis]._can_reindex(indexer)
  File "/home/ubuntu/anaconda3/envs/lab/lib/python3.6/site-packages/pandas/core/indexes/base.py", line 2944, in _can_reindex
    raise ValueError("cannot reindex from a duplicate axis")
ValueError: cannot reindex from a duplicate axis

Fix this by adding totalt as the index to append a row to eval_session_df