Monitor only response times for 2xx status

Change-Id: Ib525fca85311f0121e117f7691a0e6b48d874583
diff --git a/keystone/meta/heka.yml b/keystone/meta/heka.yml
index d046938..05fa72e 100644
--- a/keystone/meta/heka.yml
+++ b/keystone/meta/heka.yml
@@ -29,7 +29,7 @@
       - metric: openstack_keystone_http_response_times
         field:
           http_method: '== GET || == POST'
-          http_status: '!= 5xx'
+          http_status: '== 2xx'
         relational_operator: '>'
         threshold: 0.3
         window: 60