Fine tune CoreDNS pod configuration to improve performance

Make updates to the Cloud platform CoreDNS Corefile to increase
buffersize from 512 to the default of 1232.

Author: sadasu

templates/common/cloud-platform-alt-dns/files/coredns-corefile.yaml

@@ -4,10 +4,10 @@ contents:
   inline: |
     . {
         errors
-        bufsize 512
         health :18080
         forward . {{`{{- range $upstream := .DNSUpstreams}} {{$upstream}}{{- end}}`}} {
             policy sequential
+            max_concurrent 1000
         }
         cache 30
         reload