add address element in hostdev xml when the values are present

(crobins: added Guannan to AUTHORS)

Author: Guannan Ren

AUTHORS

@@ -62,6 +62,7 @@ Patches also received from
     Wanlong Gao <gaowanlong-at-cn-dot-fujitsu-dot-com>
     Eiichi Tsukata <devel-at-etsukata-dot-com>
     Gaudenz Steinlin <gaudenz-at-debian-dot-org>
+    Guannan Ren <gren-at-redhat-dot-com>
 
     ...send patches and get your name here...
 

virtinst/VirtualHostDevice.py

@@ -222,7 +222,7 @@ def _get_source_xml(self):
         if self.vendor and self.product:
             xml += "        <vendor id='%s'/>\n" % self.vendor
             xml += "        <product id='%s'/>\n" % self.product
-        elif self.bus and self.device:
+        if self.bus and self.device:
             xml += "        <address bus='%s' device='%s'/>\n" % (self.bus,
                                                                   self.device)
         else: