Write a test for re-configuring an existing persistent volume

Apparently, in the test suite we only use t-p-s to set up new persistent volumes, but we don’t test using it to configure it an existing one that was enabled in the Greeter (otherwise, #10809 (closed) would have been noticed earlier, presumably). Can we please have a simple test for that?

Feature Branch: test/10834-reconfigure-persistent-volume

Parent Task: #9476 (closed)

Related issues

Related to #10809 (closed)

Original created by @intrigeri on 10834 (Redmine)

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