"Igdenbu," the Russian silent film now at the Cameo, treats with the Goldi, a nomad tribe of Mongols, in much the same fashion as Robert J. Flaherty did with the Eskimo in his classic production, "Nanook of the North." Though the kaleidoscopic flashes give one quite an impressive conception of these people, who live on the banks of the Amur River, there is neither the clarity n...