Merge pull request autotest#5981 from Yingshun/mig_vm_nfs

migrate_vm: Fixup umount failure

libvirt/tests/cfg/migration/migrate_vm.cfg

@@ -11,10 +11,10 @@
     client_user = "root"
     client_pwd = "${migrate_source_pwd}"
     start_vm = "no"
+    storage_type =
     transport = "ssh"
     port = "22"
     client = "ssh"
-    start_vm = "no"
     ssh_port = "${port}"
     # setup NFS test environment
     nfs_client_ip = "${server_ip}"