Add host copybacks to prevent new asserts from firing. (I believe the test was failing to compare computed results previously.)
Add host copybacks to prevent new asserts from firing. (I believe the
test was failing to compare computed results previously.)

psuriana/Halide,psuriana/Halide,psuriana/Halide,psuriana/Halide,psuriana/Halide,psuriana/Halide,psuriana/Halide