fix write race condition when slot migration

[hengyoush]

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This PR fixes the issue where during slot migration(#3353 ), there might be concurrent writes of other commands between the asking command and the actual command. It achieves this by modifying the writeToChannelAndFlush(Channel channel, Collection<? extends RedisCommand> commands), changing the original method of writing to the channel using a for loop to directly writing the list to the channel, thus avoiding the aforementioned issue.