[PVE-User] Bug when removing a VM

[Dietmar Maurer]

In general, you should never mount storage on different clusters at the same
time. This is always dangerous - mostly because there is no locking and
because of VMID conflicts. If you do, mount at least read-only.

> Not sure this is a bug, but if it's not there should be a huge red
> warning in the VM removal box, I think.
> 
> We've been migrating some VMs between clusters, and for that I mounted
> the old storage on the new cluster,