Merge pull request #2266 from zhencliu/nbd_migrate

migration_with_remote_storage: support nbd

qemu/tests/cfg/migration_with_remote.cfg

@@ -2,12 +2,13 @@
 #   iscsi_direct
 #   ceph
 #   gluster_direct
+#   nbd
 # The following testing scenarios are covered:
 #   migrate VM on the same host
 #   migrate VM with postcopy on the same host
 
 - migration_with_remote_storage: install setup image_copy unattended_install.cdrom
-    only iscsi_direct ceph gluster_direct
+    only iscsi_direct ceph gluster_direct nbd
     virt_test_type = qemu
     type = migration
     migration_test_command = help