Tutorial kafka-connect-datagen-ccloud/kafka.html fails on multiple runs

In the KT, we instruct users to download and then source the ccloud_library.sh file and then call the create_ccloud_stack function.

In bash if you call a function that sets variables, they are set for the current shell, the function isn’t ran in a subshell. This will affect subsequent runs of the same function, because we look at those variable values to reuse resources.

If a user of this tutorial runs this playbook again, in the same shell, they will receive errors like the following with script hanging at the final step until timeout or the user breaks.

```
➜ CLUSTER_CLOUD=aws
CLUSTER_REGION=us-west-2
ccloud::create_ccloud_stack
Creating Confluent Cloud stack for service account demo-app-29788, ID: 113768.
Error: CCloud backend error: 1 error occurred:
* error retrieving kafka clusters: account not found
Error: unexpected CCloud backend output: protobuf unmarshalling error
Suggestions:
Please submit a support ticket.
Error: CCloud backend error: 1 error occurred:
* error listing api keys: account not found
Error: unexpected CCloud backend output: protobuf unmarshalling error
Suggestions:
Please submit a support ticket.
Waiting up to 720 seconds for Confluent Cloud cluster to be ready and for credentials to propagate
..........................................
```