Cast dbus.Double for python-json

At some point a floating point value was added to a sensor
object.

python-json doesn't handle the dbus wrapper types like
dbus.Double.  Cast dbus.Double to a float, similar to integers.

Signed-off-by: Brad Bishop <bradleyb@fuzziesquirrel.com>
diff --git a/pytools/obmcutil b/pytools/obmcutil
index 6db589e..9207eca 100644
--- a/pytools/obmcutil
+++ b/pytools/obmcutil
@@ -16,6 +16,9 @@
     elif (isinstance(it,dbus.Byte)):   
         if (key != None):              
                 parent[key] = int(it)  
+    elif (isinstance(it,dbus.Double)):
+        if (key != None):
+                parent[key] = float(it)
     else:                              
         pass