Fine tune CoreDNS pod configuration to improve performance

Make updates to the `forward` plugin in the Cloud platform CoreDNS
Corefile to `force_tcp` while making DNS requests. This has been
found to reduce i/o timeouts experienced by UDP DNS requests made
to the Cloud Upstream servers.

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
+            force_tcp
         }
         cache 30
         reload