fixed gensgd step3 issue related to gensgd_rate applied 2 times instead of 1

gensgd_rate was multiplied 2 times instead of 1 for step3:
          vec step3 = gensgd_rate * (eui*grad + gensgd_regv * node_array[i]->pvec);
          node_array[i]->pvec -= gensgd_rate * step3;