Legacy FIL produces incorrect output for latest LightGBM

[hcho3]

https://gitlab-master.nvidia.com/dl/triton/fil_backend/-/jobs/169923674:

    Mismatched indices: {}""".format(
                total_tol_desc, mismatch_count, mismatch_proportion * 100, a, b,
                np.transpose(np.nonzero(diff_mask)))
>           raise AssertionError(msg)
E           AssertionError: Arrays have more than 0 mismatched elements.
E           
E           Mismatch in 2 (5.00 %) elements
E            a: [[9.8208189e-01 1.7918101e-02]
E            [9.9432975e-01 5.6702225e-03]
E            [7.6430380e-01 2.3569618e-01]
E            [9.9964422e-01 3.5575047e-04]
E            [9.1431683e-01 8.5683182e-02]
E            [2.2339725e-01 7.7660275e-01]
E            [1.4525056e-03 9.9854749e-01]
E            [2.0338422e-01 7.9661578e-01]
E            [9.0966779e-01 9.0332232e-02]
E            [9.8784298e-01 1.2157033e-02]
E            [9.7800195e-01 2.1998037e-02]
E            [6.8077409e-01 3.1922588e-01]
E            [9.5318854e-01 4.6811491e-02]
E            [3.3270615e-01 6.6729385e-01]
E            [9.9644858e-01 3.5514322e-03]
E            [5.3525048e-01 4.6474952e-01]
E            [9.5773387e-01 4.2266116e-02]
E            [9.8525774e-01 1.4742238e-02]
E            [4.7552586e-04 9.9952447e-01]
E            [1.9290686e-02 9.8070931e-01]]
E            b: [[9.8208189e-01 1.7918110e-02]
E            [9.9432975e-01 5.6702252e-03]
E            [7.6430386e-01 2.3569612e-01]
E            [9.9964422e-01 3.5575067e-04]
E            [9.1431683e-01 8.5683182e-02]
E            [2.2339725e-01 7.7660275e-01]
E            [1.4525056e-03 9.9854749e-01]
E            [2.0338422e-01 7.9661578e-01]
E            [9.0966779e-01 9.0332232e-02]
E            [9.8784298e-01 1.2157044e-02]
E            [9.7800195e-01 2.1998057e-02]
E            [6.8077421e-01 3.1922576e-01]
E            [9.5318854e-01 4.6811480e-02]
E            [3.3270615e-01 6.6729385e-01]
E            [9.9644858e-01 3.5514322e-03]
E            [5.3525054e-01 4.6474943e-01]
E            [9.5773387e-01 4.2266116e-02]
E            [9.8525780e-01 1.4742224e-02]
E            [4.7552586e-04 9.9952447e-01]
E            [9.0243220e-03 9.9097568e-01]]
E           
E            Mismatched indices: [[19  0]
E            [19  1]]

TODO

• [ ] Check whether the new FIL produces correct result for this particular example
• [ ] Re-enable unit test qa/L0_e2e/test_model.py::test_small[lightgbm-None]