Fixed typo in routing conditions (bug 1006793)

The kwarg should be 'method' not 'methods', per Routes docs.
See: http://routes.readthedocs.org/en/latest/setting_up.html#conditions

Example in lieu of negative tests...
Without this change: http://paste.openstack.org/raw/18326/
With this change: http://paste.openstack.org/raw/18325/

Change-Id: If91fc0c79b320652674c68c433989a60c098dc1e

keystone/identity/core.py

@@ -202,7 +202,7 @@ def add_routes(self, mapper):
         mapper.connect('/tenants',
                        controller=tenant_controller,
                        action='get_tenants_for_token',
-                       conditions=dict(methods=['GET']))
+                       conditions=dict(method=['GET']))
 
 
 class AdminRouter(wsgi.ComposableRouter):