xend: Allow disable QEMU monitor by settinbg option to 0 in config file.

Signed-off-by: Daniel Kiper <dkiper@net-space.pl>

tools/python/xen/xend/image.py

@@ -376,6 +376,8 @@ class ImageHandler:
                 ret = ret + ['-monitor', vmConfig['platform'].get('monitor_path')]
             else:
                 ret = ret + ['-monitor', 'vc']
+        else:
+            ret = ret + ['-monitor', 'null']
 
         return ret