Fix containers.graph sav/get_weights
Fix containers.graph sav/get_weights

As the graph container was not using each individual layer's get/set
weights, but rather the super class layer.get_weights, which works on
self.params(), it was missing some weights in the process, i.e., the
BatchNormalizationLayer has custom get_weights which allows to save the
running mean/std. However, these running computations are not added to
BatchNormalizationLayer.params(), resulting in losing these weights
after serializing a graph model utilizing a BatchNormalizationLayer.

Fixed to use each node's get/set weights.

keras-team/keras,daviddiazvico/keras,DeepGnosis/keras,dolaameng/keras,relh/keras,kemaswill/keras,kuza55/keras,nebw/keras,keras-team/keras