Investigate QMHL test sample sensitivity

[zaqqwerty]

As the number of samples at line 46 of qmhl_loss_test.py is increased, line 269 starts to fail; for example, going from 1e6 to 1e7 samples causes the relative error to go to 0.065, whereas the tolerance is 0.02; and for 1e8 samples, relative error goes to 0.75. Faris mentioned this could be coming from an overflow somewhere.