KAFKA-12284: wait for mm2 auto-created the topic

[showuon]

The reason why the test sometimes failed with: TopicExistsException: Topic 'primary.test-topic-2' already exists. is because we tried to create the topic that the MM2 already help us created. That is,

primary.kafka().createTopic("test-topic-2", NUM_PARTITIONS);
// after the primary cluster created "test-topic-2" topic, the backup cluster will auto-created the topic: "primary.test-topic-2" for us
backup.kafka().createTopic("primary.test-topic-2", 1); // this line will have race condition with the MM2

Note: after MM2 replicate the topic, the topic partition number will also get increased to the NUM_PARTITIONS in the end. So, we should just let MM2 help us create topic. Also fix 2 issues in the tests:

1. We had resource leak due to no close the adminClient

Committer Checklist (excluded from commit message)

• Verify design and implementation
• Verify test coverage and CI build status
• Verify documentation (including upgrade notes)

[showuon]

@mimaison , could you help review this PR? Thank you.

[showuon]

@mimaison , thanks for your comments. I've addressed them and updated in this commit: de95286. Please review again. Thank you.

[mimaison]

Thanks for the PR. LGTM