xend: Fix vbd detach.

Signed-off-by: Masaki Kanno <kanno.masaki@jp.fujitsu.com>

tools/python/xen/xend/XendDomainInfo.py

@@ -607,6 +607,9 @@ class XendDomainInfo:
                     _, dev_info = sxprs[dev]
             else:  # 'vbd' or 'tap'
                 dev_info = self.getDeviceInfo_vbd(dev)
+                # To remove the UUID of the device from refs,
+                # deviceClass must be always 'vbd'.
+                deviceClass = 'vbd'
             if dev_info is None:
                 return rc