fix: band-aid around RestQueryTranslationTest

[agavra]

Description

We've had RestQueryTranslationTest fail a few times due to:

**Caused by: org.apache.kafka.common.errors.TopicExistsException: Topic 'test_topic' already exists.**

According to @big-andy-coates:

There's a race condition inherent in Kafka when deleting topics.
When you delete a topic it is delete async. Once the delete has been requested the topic info is no longer available. So no way of knowing when it's been deleted. Any attempt to recreate causes a 'topic exists' exception.

This PR simply puts a band-aid around that by retrying if there's a TopicExistsException.

Testing done

• Ran the test successfully locally and saw the log line:

[2019-09-11 10:46:29,830] WARN Retrying test after 5 SECONDS due to: Failed to create topic:test_topic (io.confluent.ksql.integration.Retry:135)

Reviewer checklist

• Ensure docs are updated if necessary. (eg. if a user visible feature is being added or changed).
• Ensure relevant issues are linked (description should include text like "Fixes #")

[stevenpyzhang]

LGTM, thanks @agavra