Fix unnecessary 'MoveErrors'

If a command timed out, try a random node, only if the command is a read command.
Write commands must only be used on the master node for the slot.

Author: JonathanWylie

rediscluster/client.py

@@ -677,7 +677,11 @@ def _execute_command(self, *args, **kwargs):
                 if ttl < self.RedisClusterRequestTTL / 2:
                     time.sleep(0.05)
                 else:
-                    try_random_node = True
+                    # If the command is not a read command, we must use the master node for the slot
+                    # otherwise we just get a MOVE response back, sending us back to the main
+                    # node.
+                    if command in READ_COMMANDS:
+                        try_random_node = True
             except ClusterDownError as e:
                 log.exception("ClusterDownError")