Implemented uuid tag on hosts

cloudcontrol/node/host/tags.py

@@ -125,6 +125,11 @@ def chaslot():
         return version.split('.')[3]
 
 
+def uuid():
+    """System UUID."""
+    return open('/sys/class/dmi/id/product_uuid').read().strip().lower() or None
+
+
 def hmodel():
     """Host hardware model."""
     return open('/sys/class/dmi/id/product_name').read().strip() or None