Sprinkle chicken with 1/8 teaspoon of the salt. For a charcoal or gas grill, place chicken on the grill rack directly over medium heat. Cover and grill for 12 to 15 minutes or until done (165 degrees F), turning once halfway through grilling. Thinly slice chicken.
In a covered large saucepan cook potatoes in enough gently boiling water to cover for 12 to 15 minutes or until tender, adding asparagus for the last 2 minutes of cooking. Drain potato mixture.
Meanwhile, in a large skillet melt butter over medium heat. Add onion and celery; cook about 5 minutes or just until tender, stirring occasionally. In a small bowl stir together the water, vinegar, chives, sugar, mustard, cornstarch, and the remaining 1/8 teaspoon salt.
Add vinegar mixture to onion mixture. Cook and stir until thickened and bubbly. Gently stir in the chicken and potato mixture. Cook, stirring gently, for 1 to 2 minutes more or until heated through. Stir in spinach and bacon before serving.