<issue_start><issue_comment>Title: Fix Rebalance events behavior when config go.application.rebalance.enable to true
username_0: The behaviour of "go.application.rebalance.enable": true appears to have changed with v1.6.1, with neither kafka.AssignedPartitions or kafka.RevokedPartitions being returned by Poll().

```
Local Test:
jliu@C02DM32YMD6T kafka % go test -run TestConsumerRebalanceEvents
EAGER rebalance: 4 new partition(s) assigned: [testConsumerRebalanceEvents[0]@unset testConsumerRebalanceEvents[1]@unset testConsumerRebalanceEvents[2]@unset testConsumerRebalanceEvents[3]@unset]
Message on testConsumerRebalanceEvents[0]@11:
Hello Go!
Headers: [time="\x01\x00\x00\x00\x0e\xd80\xddR\x1e>\x18\x90\xfe\\"]
Consumer closed

COOPERATIVE rebalance: 4 new partition(s) assigned: [testConsumerRebalanceEvents[0]@unset testConsumerRebalanceEvents[1]@unset testConsumerRebalanceEvents[2]@unset testConsumerRebalanceEvents[3]@unset]
Message on testConsumerRebalanceEvents[0]@12:
Hello Go!
Headers: [time="\x01\x00\x00\x00\x0e\xd80\xddS\x00mc\xe8\xfe\\"]
Consumer closed

COOPERATIVE rebalance: 4 new partition(s) assigned: [testConsumerRebalanceEvents[0]@unset testConsumerRebalanceEvents[1]@unset testConsumerRebalanceEvents[2]@unset testConsumerRebalanceEvents[3]@unset]
Message on testConsumerRebalanceEvents[0]@13:
Hello Go!
Headers: [time="\x01\x00\x00\x00\x0e\xd80\xdd[\x00\xa6}\x18\xfe\\"]
COOPERATIVE rebalance: 4 partition(s) revoked: [testConsumerRebalanceEvents[0]@unset testConsumerRebalanceEvents[1]@unset testConsumerRebalanceEvents[2]@unset testConsumerRebalanceEvents[3]@unset]
Consumer closed

EAGER rebalance: 4 new partition(s) assigned: [testConsumerRebalanceEvents[0]@unset testConsumerRebalanceEvents[1]@unset testConsumerRebalanceEvents[2]@unset testConsumerRebalanceEvents[3]@unset]
Message on testConsumerRebalanceEvents[0]@14:
Hello Go!
Headers: [time="\x01\x00\x00\x00\x0e\xd80\xdd[\x1en\x15\xb8\xfe\\"]
EAGER rebalance: 4 partition(s) revoked: [testConsumerRebalanceEvents[0]@unset testConsumerRebalanceEvents[1]@unset testConsumerRebalanceEvents[2]@unset testConsumerRebalanceEvents[3]@unset]
Consumer closed
PASS
ok  	kafka	0.259s
```
<issue_comment>username_1: Is there an approximate date/timeline on where this fix will be landed and rolled out? possibly to `1.6.2`?
<issue_comment>username_2: This will be released in v1.8.0, scheduled for august.
<issue_comment>username_1: @username_2 Is it possible to backport this fix to the `1.6.x` versions? That would be very helpful from the Robinhood's perspective
<issue_comment>username_0: Hi @username_1, thanks for asking, since we didn't release bug fix in this way before, we are discussing about this and update soon.
<issue_comment>username_0: @username_1 , sorry for the late response, we will update to you early next week
<issue_comment>username_0: @username_1, after discussing with the team, we never backport any fix before. I'm really sorry for the inconvenience.  Please feel free to let us know if anything else we can help.
<issue_comment>username_2: Can you force push to this branch to re-trigger CI?
<issue_comment>username_3: So if I understand this correctly, `go.application.rebalance.enable` is currently broken from >= 1.6? How do we handle rebalance requests then?
<issue_comment>username_4: Is there an approximate timeline on where this fix will be landed and rolled out?