Extend buffer for the telegraf openstack output plugin

Change-Id: I8dd00593e0253c893ddc5d6b98d836f5f63e5f6b
Related-PROD: PROD-27908
(cherry picked from commit 1df4c20043874180b1251090c407f8ce2ee2de3a)
diff --git a/keystone/meta/telegraf.yml b/keystone/meta/telegraf.yml
index 476703e..2c25702 100644
--- a/keystone/meta/telegraf.yml
+++ b/keystone/meta/telegraf.yml
@@ -18,6 +18,7 @@
     prometheus_client_openstack:
       template: telegraf/files/output/prometheus_client.conf
       engine: prometheus
+      metric_buffer_limit: 50000
       # Output plugin configuration
       bind:
         address: 0.0.0.0