Add applications to groups only if postfix is defined

If applications_postfix is not set, then the groups list should only be
the classes list. Else there might be naming conflicts.

In any case, applications_postfix is probably not going to stay, so this
is a hack.

Signed-off-by: martin f. krafft <madduck@madduck.net>
diff --git a/reclass/storage/__init__.py b/reclass/storage/__init__.py
index 203d2d2..1d26874 100644
--- a/reclass/storage/__init__.py
+++ b/reclass/storage/__init__.py
@@ -41,7 +41,9 @@
     def inventory(self):
         entities, applications, classes = self._list_inventory()
         groups = classes.copy()
-        groups.update([(k + self._applications_postfix,v) for k,v in applications.iteritems()])
+        if self._applications_postfix:
+            groups.update([(k + self._applications_postfix,v) for k,v in
+                           applications.iteritems()])
         return {'__reclass__' : {'timestamp': _get_timestamp(),
                                  'application_postfix': self._applications_postfix},
                 'nodes': entities,