Handling key exceptions on the variable itself

This is the first step towords to solve #1697

src/variables/xml.cc

@@ -137,8 +137,10 @@ void XML::evaluate(Transaction *t,
             std::string *a = new std::string(content);
             VariableValue *var = new VariableValue(m_fullName,
                 a);
+            if (!m_keyExclusion.toOmit(*m_fullName)) {
+                l->push_back(var);
+            }
             delete a;
-            l->push_back(var);
             xmlFree(content);
          }
     }