Load XOS certificates from files rather than embedding in the values file

Change-Id: Iebcba439adfdb8e9358067a0e84ab790b39a17d4
diff --git a/xos-core/templates/_core.tpl b/xos-core/templates/_core.tpl
index 6722475..bd13e16 100644
--- a/xos-core/templates/_core.tpl
+++ b/xos-core/templates/_core.tpl
@@ -69,6 +69,6 @@
 {{- end }}
 
 {{- define "xos-core.ca_cert_chain" }}
-{{ .Values.ca_cert_chain | b64dec }}
+{{ (.Files.Get "pki/xos-CA.pem")}}
 {{- end }}