[MRG+1] FIX heisenfailure in test_lasso_lars_path_length

Tentative fix for #3370: random failure under Python 32 bit and Windows.

The failure is very rare so I am not 100% sure that this fixes it. Appveyor will tell over time. In the mean time I do a PR here to have travis check that this does not cause a failure in some other test.