<fix>[vm_config]: fix config port skip hostname if no exist

Resolves: ZSTAC-69187

Change-Id:I6868776c51c9e5f2fc3d4540a5d730a3993a304a

Author: bustezero

kvmagent/kvmagent/plugins/vm_config.py

@@ -250,12 +250,13 @@ def vm_config_ports(self, req):
             rsp.error = msg
         else:
             logger.debug("config vm {} by qga successfully, detail info {}".format(cmd.vmUuid, msg))
-            ret, msg = self.set_vm_hostname_by_qga(domain, cmd.hostname, cmd.defaultIP)
-            if ret != 0:
-                rsp.success = False
-                rsp.error = msg
-            else:
-                logger.debug("config vm {} by qga successfully, detail info {}".format(cmd.vmUuid, msg))
+            if cmd.hostname:
+                ret, msg = self.set_vm_hostname_by_qga(domain, cmd.hostname, cmd.defaultIP)
+                if ret != 0:
+                    rsp.success = False
+                    rsp.error = msg
+                else:
+                    logger.debug("config vm {} hostname {} by qga successfully, detail info {}".format(cmd.vmUuid, cmd.hostname, msg))
 
         return jsonobject.dumps(rsp)