Conf test for Bulk Subscribe and Kafka fixes

[DeepanshuA]

Description

Intends to add Conf Tests for Bulk Subscribe Implementation. While writing bulkSubscribe Conf tests, found out 2 issues with Kafka bukSubscribe implementation, so fixing those with this PR itself:

1. There was an issue while concurrently subscribing on one topic and bulkSubscribing on another topic.
2. Issue was there in ConsumeClaim where-in for bulkSubscribe topic messages, old method processBulkMessages was returning and thus ConsumeClaim was called again, it led to failure of Conf Test for PubSub where-in few messages (1, 2 and 5 out of 10 messages are failed for few times).

These issues are fixed.

Issue reference

We strive to have all PR being opened based on an issue, where the problem or feature have been discussed prior to implementation.

Please reference the issue this PR is linked to: https://github.com/dapr/dapr/issues/2218

Checklist

Please make sure you've completed the relevant tasks for this PR, out of the following list:

• [ ] Code compiles correctly
• [ ] Created/updated tests
• [ ] Extended the documentation / Created issue in the https://github.com/dapr/docs/ repo: dapr/docs#[issue number]