App. Explorer "hangs" on extension loading if logged out from a cluster

[vrubezhny]

When Kube config's current-context points to a cluster which is available, but a user is not logged in to, the extension fails to load the App. explorer initial content permanently staying in "loading..." state.

Steps to reproduce:

• Log in to "http:/api-rhamilto-devcluster-openshift-com:6443" cluster, see the default project and its contents loaded and shown in App. Explorer
• Log out from the cluster, see "Login" button appeared instead of the App. Explorer tree
• Exit VSCode Openshift Tools
• Stat again, Fail: see the "infinite" loading of App. Explorer

This probably happens because the kubectl utilities, when invoked, are "permanently" waiting for user input:

$ kubectl cluster-info
Please enter Username: 

$ kubectl api-versions
Please enter Username:

The issue was highly likely introduced by this commit