Fix timeout in Kafka test

Instead of waiting for some time and then check whether messages have
been consumed, this fix waits for exactly one message to be consumed.
Additionally, a timeout of 30s ist set to not wait forever in case of
a failing test.

charts/cp-kafka/templates/tests/canary-pod.yaml

@@ -23,5 +23,5 @@ spec:
       # Produce a test message to the topic
       echo "$MESSAGE" | kafka-console-producer --broker-list {{ template "cp-kafka.fullname" . }}:9092 --topic {{ template "cp-kafka.fullname" . }}-canary-topic && \
       # Consume a test message from the topic
-      kafka-console-consumer --bootstrap-server {{ template "cp-kafka.fullname" . }}-headless:9092 --topic {{ template "cp-kafka.fullname" . }}-canary-topic --from-beginning --timeout-ms 2000 | grep "$MESSAGE"
+      kafka-console-consumer --bootstrap-server {{ template "cp-kafka.fullname" . }}-headless:9092 --topic {{ template "cp-kafka.fullname" . }}-canary-topic --from-beginning --max-messages 1 --timeout-ms 30000 | grep "$MESSAGE"
   restartPolicy: Never