replace `chunk.hasRuntime` with `chunk.parents.length === 0`

see https://github.com/webpack/webpack/pull/4310\#discussion_r102400692

lib/optimize/CommonsChunkPlugin.js

@@ -244,7 +244,7 @@ Take a look at the "name"/"names" or async/children option.`);
 		return allChunks.filter((chunk) => {
 			const found = targetChunks.indexOf(chunk);
 			if(found >= currentIndex) return false;
-			return chunk.hasRuntime();
+			return chunk.parents.length === 0;
 		});
 	}