Heat oil in a large saucepan over medium heat. Cook onion, garlic, and jalapenos in oil until lightly browned, 4 to 5 minutes. Stir in chicken, chicken broth, lime juice, tomato, salt and pepper. Gently simmer until chicken is no longer pink, about 10 minutes. Stir in avocado and cilantro and heat through, 3 to 5 minutes. Adjust seasonings to taste.