When a user migrates a domain by command as

libvirt saves vm's domain XML config in destination host after migration.
But it saves vm->def. Then, the saved XML contains some garbage.

  <domain type='kvm' id='50'>
                     ^^^^^^^^
  ...
   <console type='pty' tty='/dev/pts/5'>
                       ^^^^^^^^^^^^^^^^^

Avoid saving unnecessary things by saving persistent vm definition.