Fix auth_token for old oslo.config

When running with a havana-level of oslo.config (<1.3.0),
applications with any config options in their api-paste.ini will
fail to start with an error like

 'StrOpt' object has no attribute 'type'

This is because the config options didn't have a type attribute
until 1.3.0.

During the grenade test, the havana level of oslo.config is used.

Change-Id: I745c3e04f18941a2d41e191d43f61b926522bb9d
Closes-Bug: #1372422

keystonemiddleware/auth_token.py

@@ -440,7 +440,7 @@ def _conf_values_type_convert(conf):
     if not conf:
         return {}
     opts = {}
-    opt_types = dict((o.dest, o.type) for o in _OPTS)
+    opt_types = dict((o.dest, getattr(o, 'type', str)) for o in _OPTS)
     for k, v in six.iteritems(conf):
         try:
             if v is None: