Use first the dotted name variable in the PYSON context

issue11109
review383991002
(grafted from 7121bacd50e12369b68e3152398238d0f744a468)

--HG--
branch : 6.0

tryton/pyson.py

@@ -153,7 +153,7 @@ class Eval(PYSON):
 
     @staticmethod
     def eval(dct, context):
-        if '.' in dct['v']:
+        if '.' in dct['v'] and dct['v'] not in context:
             base, name = dct['v'].split('.', 1)
             return Eval.eval({
                     'v': name,