virt-manager: Disable storage test

pkgs/applications/virtualization/virt-manager/default.nix

···
     "tests/test_cli.py"
     "tests/test_disk.py"
     "tests/test_checkprops.py"
+    "tests/test_storage.py"
   ]; # Error logs: https://gist.github.com/superherointj/fee040872beaafaaa19b8bf8f3ff0be5
 
   preCheck = ''