etcd chart: anchor pre_stop remove bashism

The anchor pre-stop script uses the 'function' command, which fails when
using dash. This change removes it for compatibility.

Change-Id: I6591045fa0a555800a03edbdf1f9f3a8476dd0a3

charts/etcd/templates/bin/_pre_stop.tpl

@@ -15,7 +15,7 @@
 
 set -ex
 
-function cleanup_host {
+cleanup_host () {
     rm -f $MANIFEST_PATH
     rm -rf /etcd-etc/tls/
     {{- if .Values.etcd.cleanup_data }}