storage: Add duplicate devices check for zfs pool def
storage: Add duplicate devices check for zfs pool def

Check proposed pool definitions to ensure they aren't trying to use the
same devices as currently defined definitions - disallow the duplicate

VenkatDatta/libvirt,nertpinx/libvirt,fabianfreyer/libvirt,datto/libvirt,jardasgit/libvirt,taget/libvirt,olafhering/libvirt,olafhering/libvirt,eskultety/libvirt,zippy2/libvirt,eskultety/libvirt,libvirt/libvirt,andreabolognani/libvirt,jfehlig/libvirt,crobinso/libvirt,taget/libvirt,jfehlig/libvirt,fabianfreyer/libvirt,jardasgit/libvirt,eskultety/libvirt,libvirt/libvirt,VenkatDatta/libvirt,agx/libvirt,taget/libvirt,agx/libvirt,datto/libvirt,crobinso/libvirt,jfehlig/libvirt,zippy2/libvirt,crobinso/libvirt,jardasgit/libvirt,taget/libvirt,andreabolognani/libvirt,nertpinx/libvirt,VenkatDatta/libvirt,rlaager/libvirt,agx/libvirt,olafhering/libvirt,datto/libvirt,taget/libvirt,rlaager/libvirt,crobinso/libvirt,zippy2/libvirt,datto/libvirt,VenkatDatta/libvirt,zippy2/libvirt,rlaager/libvirt,nertpinx/libvirt,agx/libvirt,eskultety/libvirt,agx/libvirt,datto/libvirt,nertpinx/libvirt,jardasgit/libvirt,andreabolognani/libvirt,fabianfreyer/libvirt,andreabolognani/libvirt,eskultety/libvirt,libvirt/libvirt,jardasgit/libvirt,olafhering/libvirt,fabianfreyer/libvirt,rlaager/libvirt,andreabolognani/libvirt,rlaager/libvirt,jfehlig/libvirt,libvirt/libvirt,VenkatDatta/libvirt,fabianfreyer/libvirt,nertpinx/libvirt