Move tempest to oslo-config-generator

Also fixes tempest reported bug with old generator in oslo-incubator,
when identical options are registered in different groups.

Change-Id: I274f48503c1b61ca09cabc8d8c50245ba1059943
Closes-bug: 1282887
diff --git a/setup.cfg b/setup.cfg
index 2e25ace..d010ccc 100644
--- a/setup.cfg
+++ b/setup.cfg
@@ -24,6 +24,9 @@
     run-tempest-stress = tempest.cmd.run_stress:main
     tempest-cleanup = tempest.cmd.cleanup:main
 
+oslo.config.opts =
+    tempest.config = tempest.config:list_opts
+
 [build_sphinx]
 all_files = 1
 build-dir = doc/build