Doc: Improvements to Getting Started in AMQ Streams on RHEL doc

In the Getting Started chapter of Using AMQ Streams on RHEL (https://access.redhat.com/documentation/en-us/red_hat_amq/7.5/html/using_amq_streams_on_rhel/assembly-getting-started-str), all of the procedures worked for me as documented. However, I did notice several points of confusion that could be improved to make it easier to follow.

2.5. Running single node AMQ Streams cluster:

• For the verification steps (3 and 6) that involve grepping, it would be helpful to show the expected output.

2.6. Using the cluster:

• This procedure assumes you're already in the /opt/kafka/ dir. It would be helpful to show or state that.
• For step 3, you might want to mention any error/warning logs you might see when you press Enter. I got the following warnings, and wasn't sure at first if I could ignore them (since it's just a simple getting started exercise), or if I did something wrong:

[2020-01-27 15:40:12,290] WARN [Producer clientId=console-producer] Error while fetching metadata with correlation id 3 :

{my-topic=LEADER_NOT_AVAILABLE} (org.apache.kafka.clients.NetworkClient)
[2020-01-27 15:40:12,392] WARN [Producer clientId=console-producer] Error while fetching metadata with correlation id 4 : {my-topic=LEADER_NOT_AVAILABLE}

(org.apache.kafka.clients.NetworkClient)