add rbd with luks scenario in blockcopy with dest xml case

[nanli1]

xxxx-294410: Do blockcopy with different dest XML - rbd with luks and auth Signed-off-by: nanli [email protected]

avocado run --vt-type libvirt --test-runner=runner --vt-machine-type q35 backingchain.blockcopy.dest_xml.rbd_with_luks_and_auth
 (1/1) type_specific.io-github-autotest-libvirt.backingchain.blockcopy.dest_xml.rbd_with_luks_and_auth.pivot_reuse_external: PASS (56.15 s)
 (1/1) type_specific.io-github-autotest-libvirt.backingchain.blockcopy.dest_xml.rbd_with_luks_and_auth.finish_reuse_external: PASS (61.22 s)

Got error on rhel10 ,yalan is confirming

2024-07-07 21:47:09,652 virsh            L0822 DEBUG| Running virsh command: blockcopy avocado-vt-vm1 vdb  --pivot  --xml /tmp/xml_utils_temp_jjulza25.xml --transient-job --reuse-external --verbose --wait
2024-07-07 21:47:09,652 process          L0658 INFO | Running '/bin/virsh blockcopy avocado-vt-vm1 vdb  --pivot  --xml /tmp/xml_utils_temp_jjulza25.xml --transient-job --reuse-external --verbose --wait '
2024-07-07 21:47:09,839 process          L0470 DEBUG| [stderr] error: internal error: unable to execute QEMU command 'blockdev-add': encryption load fail: Invalid argument