Close as ERRATA

See https://fedoraproject.org/wiki/BugZappers/BugStatusWorkFlow

Fixes #427.

bodhi/bugs.py

@@ -114,7 +114,7 @@ def close(self, bug_id, versions):
                 # - space-separated if there's more than one.
                 args['fixedin'] = " ".join(fixedin)
 
-            bug.close('NEXTRELEASE', **args)
+            bug.close('ERRATA', **args)
         except xmlrpclib.Fault:
             log.exception("Unable to close bug #%d" % bug_id)