I Love Country Cafe   At these restaurants popular with athletes, bodybuilders and others who closely watch their diets, you can get anything from a virtually fatless vegetarian meal to a standard, gravy-over-everything plate it's your call. The service is fast, the items are grilled to order, and there are numerous daily specials. The menu is typically local with lots of stir-fries and other Asian-style preparations. They cater, too.  Kaka'ako: 451 Pi'ikoi St. 596-8108. 8 a.m.-9 p.m. daily. Pearl Harbor: Pearl Harbor Navy Exchange. 423 6555, 7 a.m.-9 p.m. daily. Kane'ohe: Windward Mall, 236-3688. 9 a.m. 9 p.m. daily. No reservations.