Construct the Record.expr_eval context the same way as tryton

issue5122
review23641002

src/model.js

@@ -1019,8 +1019,9 @@
         },
         expr_eval: function(expr) {
             if (typeof(expr) != 'string') return expr;
-            var ctx = jQuery.extend({}, this.get_context());
-            ctx.context = jQuery.extend({}, this.model.session.context, ctx);
+            var ctx = jQuery.extend({}, this.model.session.context);
+            ctx.context = jQuery.extend({}, ctx.context);
+            jQuery.extend(ctx.context, this.get_context());
             jQuery.extend(ctx, this.get_eval());
             ctx.active_model = this.model.name;
             ctx.active_id = this.id;