chore(init) use bash for migrations check

Use bash instead of sh for the migrations check. The default sh in the
new 3.x Debian default images is incompatible with some scripts. This
script is likely compatible, but we want to use bash across the board
for consistency.

charts/kong/templates/_helpers.tpl

@@ -605,7 +605,7 @@ The name of the service used for the ingress controller's validation webhook
   {{- include "kong.env" . | nindent 2 }}
 {{/* TODO the prefix override is to work around https://github.com/Kong/charts/issues/295
      Note that we use args instead of command here to /not/ override the standard image entrypoint. */}}
-  args: [ "/bin/sh", "-c", "export KONG_NGINX_DAEMON=on KONG_PREFIX=`mktemp -d` KONG_KEYRING_ENABLED=off; until kong start; do echo 'waiting for db'; sleep 1; done; kong stop"]
+  args: [ "/bin/bash", "-c", "export KONG_NGINX_DAEMON=on KONG_PREFIX=`mktemp -d` KONG_KEYRING_ENABLED=off; until kong start; do echo 'waiting for db'; sleep 1; done; kong stop"]
   volumeMounts:
   {{- include "kong.volumeMounts" . | nindent 4 }}
   {{- include "kong.userDefinedVolumeMounts" .Values.deployment | nindent 4 }}