Move tenant_config option to scheduler section

This is only used by the scheduler and makes more sense here.

Change-Id: I85009894fd5bd02e8795d59ea2a2612b46941718
diff --git a/tests/fixtures/zuul.conf b/tests/fixtures/zuul.conf
index c4cfe70..d6de76c 100644
--- a/tests/fixtures/zuul.conf
+++ b/tests/fixtures/zuul.conf
@@ -1,7 +1,7 @@
 [gearman]
 server=127.0.0.1
 
-[zuul]
+[scheduler]
 tenant_config=main.yaml
 
 [merger]