If the libvirt mount point is still busy and can't be unmounted
right now, it was waited 5 seconds and an plain unmount was tried,
without cleaning up the libvirt storagepool.
This kept libvirt thinking the storagepool
is active and mounted (which it wasn't).
Now after the plain unmount call, also
the libvirt storagepool will be destroyed.
21f3fde7b4