Bob Moyer knows New Orleans, and he knows good police procedurals. He finds much to praise in this lively novel. Reviewed by Robert P. Moyer THE DEVIL’S MUSE. By Bill Loehfelm. Farrar Straus Giroux. 258 pages. $26. Mardi Gras. Most people see a chance to party, beads flying through the air, beads on the ground,…