ENH 13 more examples fixed with matplotlib 2.0 (#9029)

...s/cross_decomposition/plot_compare_cross_decomposition.py

examples/datasets/plot_iris_dataset.py

examples/datasets/plot_random_dataset.py

examples/decomposition/plot_kernel_pca.py

examples/ensemble/plot_adaboost_twoclass.py

examples/ensemble/plot_forest_iris.py

examples/ensemble/plot_isolation_forest.py

examples/ensemble/plot_partial_dependence.py

examples/ensemble/plot_random_forest_embedding.py

...les/ensemble/plot_random_forest_regression_multioutput.py

examples/ensemble/plot_voting_decision_regions.py

examples/ensemble/plot_voting_probas.py

examples/exercises/plot_iris_exercise.py