Provide a warning if MAS CLI must-gather is running without being logged into a cluster

[BrendanFishback]

Feature and motivation

Currently, when a MAS CLI must-gather is run without logging into a OpenShift cluster, the must-gather will still execute and attempt to collect data. The collection logs will be full of messages like this:

error: Missing or incomplete configuration info.  Please point to an existing, complete config file:

  1. Via the command-line flag --kubeconfig
  2. Via the KUBECONFIG environment variable
  3. In your home directory as ~/.kube/config

While to someone experienced with OpenShift this may be an obvious sign the must-gather did not collect the data properly, it is not immediately apparent to those with less exposure to OpenShift. It would be beneficial if the must-gather script itself would provide a warning message to the end user that the must-gather did not execute properly due to not being logged in to a cluster instead.

Usage example

This would save time from having to request data multiple times from clients with less experience with OpenShift.