Description of problem:
This is a regression coming from [1]. In enabling the OpenShift Console to search all namespaces for a Web Terminal Operator installation, the logic for checking if the operator is installed was changed from

  "Get subscriptions.operators.coreos.com 
   in namespace openshift-operators named 'web-terminal'"

to

  "List subscriptions.operators.coreos.com 
   in cluster named 'web-terminal'"

In the first case, the API returns "not found" if the subscription does not exist. However, in the updated check, the API will return an empty list instead. The console still checks for the "not found" response, and so misses that the list of subscriptions is empty and assumes the operator is present.

There are further checks that the console does, so in most cases the request to the `/api/terminal/available` endpoint still returns the correct result. However, if the cluster has the DevWorkspace Operator installed independently of the Web Terminal Operator [2], these further checks succeed and the Web Terminal UI button is shown incorrectly.

[1] - https://bugzilla.redhat.com/show_bug.cgi?id=2006329
[2] - Background: the DevWorkspace Operator is a dependency of the Web Terminal Operator that provides required webhooks and custom resource definitions.


Version-Release number of selected component (if applicable): 4.8, 4.9, 4.10


How reproducible: Always


Steps to Reproduce:
1. Install the DevWorkspace Operator in the cluster via OperatorHub
2. Refresh OpenShift Console web page


Actual results:
* Web Terminal button is visible in top-right ('>_').
* Browser network requests during page load returns HTTP 204 for /api/terminal/available.

Expected results:
* Console backend does not return HTTP 204 until Web Terminal Operator is installed.
* Web Terminal button is not present in UI until Web Terminal Operator is installed.

Additional info: