The Christian Science Monitor January 20, 1988, Wednesday By Amy Duncan SINEAD O'CONNOR * ''The Lion and the Cobra'' (Chrysalis Records BFV 41612) - O'Connor is a talented new rock singer/-songwriter from Ireland. Her debut album is uneven, startling, intriguing, and powerful. Her voice ranges from a raw, rough wail to a sweet whisper, and the moods vary just as wildly. If O'Connor seems overly dramatic at times, she more than makes up for it with her acute musical