`rhmas kafka list` does not display anything when there is no Kafka clusters

[machi1990]

We should at least display a message saying that the current user has no kafka clusters.

To reproduce -

change the results in https://github.com/bf2fc6cc711aee1a0c2a/cli/blob/dd3692b9d2e993fefd90db1afcc097e45f6ce306/mas-mock/src/handlers.js#L57 to return an empty list.

Start the mock-server

cd mas-mock
yarn 
yarn start

build the cli and then ./rhmas kafka list.

see attached image

The first command corresponds to what we have when there is something returned from the list.

The second command returns blank since the list is empty (this is a bug).
/cc @craicoverflow @wtrocki

[wtrocki]

+100!