You read in some magazine once that every good hostess should always have a few key items on hand for spontaneous entertaining. Then you promptly went out and bought a jar of olives, several boxes of crackers, some quince paste or exotic honey and a few other obscure pantry items. It felt good to know that if you ran into someone on the street you could say, "Come on in for a glass of wine." You were so organized and ready! Yeah, that was four years and two apartments ago, and you've packed up and moved the margarita mix and salt from one pantry to the next. Let's face it, you're either antisocial, or when you entertain you always end up shopping for fresh ingredients. No matter how you slice it, those olives have got to go.