fix leaked nack tracker goroutine

[zzzming]

Motivation

The negative ack tracker, nackTracker, created by consumer_partition has leaks in many places. These goroutines left running even after the consumers are Close().

Modifications

1. Close the nackTracker in each failure path on partition consumer creation.
2. Only send close sig once to nackTracker goroutine.
3. Close the nackTracker in consumer notready state too. (this may not need at the current implementation since we use sync.Once to close the tracker thread. It prevents leaks in the future).

Verifying this change

Does this pull request potentially affect one of the following parts:

If yes was chosen, please highlight the changes

• Dependencies (does it add or upgrade a dependency): no
• The public API: no
• The schema: no
• The default values of configurations: no
• The wire protocol: no

Documentation

• Does this pull request introduce a new feature? no
• If yes, how is the feature documented?
• If a feature is not applicable for documentation, explain why?
• If a feature is not documented yet in this PR, please create a followup issue for adding the documentation