The issue was that, sometimes, the ID generated for one of the nodes
contained the slot ID that was used in the test (either 5259 or 5260).
This caused the test to replace the "slot" part of the id, which in turn
caused the node to think that it no longer owns any slot.
In this case, `redis.RedisCluster`.
To be double sure I also looked at the actual packets and saw that the
client asks for `CLUSTER SLOTS`, and then after the redistribution of
slots, following a few `MOVED` replied, it asks for the new slots again.
This allows masters to send data of non-owned keys to their replicas,
which is useful when:
1. Config is temporarily different between master and replica
2. Preparing for taking ownership over currently not-owned slots (in the upcoming migration feature)
Fixed#1319
