In a liquid measuring cup, combine the vinegar, shallots, and one teaspoon salt. Set aside. Meanwhile, cut off and discard the top third of the garlic head, leaving the head intact. In a 2-quart saucepan over medium-high, combine the garlic, water, carrots, celery, mustard seeds, thyme, bay leaves, and one teaspoon salt. Bring to a boil, then cover, reduce heat to low and simmer for 30 minutes. Remove and discard the carrot, celery, thyme and bay leaves.