GLM: Plug values don't respect standardization

[tomasfryda]

It appears that Plug Values are not standardized even when standardize=True is set which I think should be considered a bug - it makes it really hard to impute, e.g., median since the user would first have to standardize the frame and then calculate the median value from that without knowing if the standardization yielded the same values since we do it internally and I don't think we show the values anywhere).

Steps to reproduce

h2o_iris <- as.h2o(iris)

glm_model_plug_values_standardized <- h2o.glm(y="Sepal.Length",
                                              training_frame=h2o_iris,
                                              missing_values_handling="PlugValues",
                                              plug_values=as.h2o(data.frame(
                                                Sepal.Width=0,
                                                Petal.Length=0,
                                                Petal.Width=0,
                                                Species="versicolor")),
                                              standardize = TRUE)
# Standardized model
glm_model_plug_values_standardized@model$coefficients
# Intercept     Species.setosa Species.versicolor  Species.virginica        Sepal.Width       Petal.Length        Petal.Width 
# 1.5834912          0.5716142          0.0000000         -0.2420645          0.5199133          0.7813752         -0.3135125 
h2o_iris[,c(-4,-5)]
#   Sepal.Length Sepal.Width Petal.Length
# 1          5.1         3.5          1.4
# 2          4.9         3.0          1.4
# 3          4.7         3.2          1.3
# 4          4.6         3.1          1.5
# 5          5.0         3.6          1.4
# 6          5.4         3.9          1.7

# Intercept + b_SW*SW + b_PL*PL  (and -0.3135125 * 0 (0 is the plug value; otherwise it would be 0.2) + 0 for versicolor)
abs(1.5834912+0.5199133*3.5+0.7813752*1.4 - predict(glm_model_plug_values_standardized, h2o_iris[,c(-4,-5)])[1]) # => 4.067362e-08

Obviously, Petal.Width == 0 is an outlier and as such it should influence the GLM a lot but since there is no standardization of plug values it gets interpreted as already standardized value and does not contribute to the prediction at all (multiplication of β by zero).