DISTURBANCE-LOVING SPECIES By Peter Chilson (Mariner Books, 240 pages, $13.95) Somewhere out beyond the markers placed by Joseph Conrad and Isak Dinesen is the reality of Africa, a continent and its peoples at once vibrant and terrible, but somehow just beyond the reach of even the keenest foreign imagination. That fraught disjunction is what animates Peter Chilson’s first collection of short …