http://kennethdalbjerg.dk/2012/10/11/xenserver-moving-vm-vdiname-to-vdiname-on-storage-this-operation-cannot-be-performed-because-this-vdi-opaqueref8d37bee1-f85b-fb22-e47e-1b8f48b68b84-is-in-use-by-some-other-operation-c