In a large pot, cook the kielbasa and onion over medium heat until the onion is tender, about 10 minutes. Stir in the mustard and vinegar, then add the chicken broth, potatoes and coleslaw mix; season with salt and pepper. Bring to a boil, then lower the heat and simmer until the potatoes are tender, 15 to 20 minutes. Stir in the parsley and season with salt and pepper. Serve with the bread.