NSQ HA 1.12.6

1. fix load channel should not persist the init meta which will cause the state lost for the channel if exit by unexpected.
2. handle the message which timeout too much to avoid blocking too long
3. add the experimental kv-index for the topic (disabled by default).
4. clean check max available if can not greedy clean directly
5. return an error if update channel state or delete channel failed to sync