virsh: reject undefine --wipe-storage without also naming storage
    
    For now, if only '--wipe-storage' is assigned, user can undefine a
    domain normally. But actually '--wipe-storage' doesn't do anything,
    and this may confuse user. Better is to require that '--wipe-storage'
    only works if the user specifies volumes to be removed.
    
    Before:
    $ virsh undefine virt-tests-vm1 --wipe-storage
    Domain virt-tests-vm1 has been undefined
    
    After:
    $ virsh undefine virt-tests-vm1 --wipe-storage
    error: '--wipe-storage' requires '--storage <string>' or '--remove-all-storage'
    
    Signed-off-by: Li Yang <liyang.fnst@cn.fujitsu.com>
    Signed-off-by: Eric Blake <eblake@redhat.com>