tests: Fix in Marvin migrate_vm_with_volume (#5023)

Cannot migrate VM to another storage, because 'migrateto' is overriden.

Author: slavkap

tools/marvin/marvin/lib/base.py

@@ -867,8 +867,8 @@ def migrate_vm_with_volume(self, apiclient, hostid=None, migrateto=None):
         if hostid:
             cmd.hostid = hostid
         if migrateto:
-            migrateto = []
-            for volume, pool in migrateto.items():
+            cmd.migrateto = []
+            for volume, pool in list(migrateto.items()):
                 cmd.migrateto.append({
                     'volume': volume,
                     'pool': pool