Fix generate-uuid implementation to use randomUUID

generate-uuid is using `new UUID(random.nextLong(), random.nextLong()) ` to generate UUID. This is resulting in UUID conflicts probably because Random.nextLong() doesn't return the full set of possible longs. (From the java docs - Because class Random uses a seed with only 48 bits, this algorithm will not return all possible long values). Use UUID.randomUUID() instead.