Migration left the VM defined on the source host unless "Delete
original" was ticked (VIR_MIGRATE_UNDEFINE_SOURCE). With the shared
storage migration needs, that definition points at the disks the
destination VM is running on: the VM showed on both hosts and could be
started (or autostarted) a second time against the same disks; only a
configured lock manager stops that.
moveto now always passes VIR_MIGRATE_UNDEFINE_SOURCE with
VIR_MIGRATE_PERSIST_DEST. The option is gone from the form, the view,
the API (MigrateSerializer.xml_del) and the clone auto-migration. It
removes the definition, not the disk files.
