Alphabetically sort list of super users (#291)

Fixes #288 

### Motivation

When specifying multiple roles in `.Values.auth.superUsers` the values are converted to a comma-separated list by piping the dict through `values` and `join` in helm templating, `values` however doesn't guarantee that the order of elements will be the same every time. Therefor it recommends also passing it through `sortAlpha` to sort the list alphabetically.

This is a problematic when `.Values.broker.restartPodsOnConfigMapChange` is enabled because the checksum of the configmap changes every time the list's order is changed, resulting in the statefulsets rolling out a new version of the pods.

### Modifications

Pass list through `sortAlpha`.

### Verifying this change

- [x] Make sure that the change passes the CI checks.

charts/pulsar/templates/broker-configmap.yaml

@@ -110,7 +110,7 @@ data:
   authenticationEnabled: "true"
   {{- if .Values.auth.authorization.enabled }}
   authorizationEnabled: "true"
-  superUserRoles: {{ .Values.auth.superUsers | values | join "," }}
+  superUserRoles: {{ .Values.auth.superUsers | values | sortAlpha | join "," }}
   {{- end }}
   {{- if eq .Values.auth.authentication.provider "jwt" }}
   # token authentication configuration

charts/pulsar/templates/proxy-configmap.yaml

@@ -64,7 +64,7 @@ data:
   # disable authorization on proxy and forward authorization credentials to broker
   authorizationEnabled: "false"
   forwardAuthorizationCredentials: "true"
-  superUserRoles: {{ .Values.auth.superUsers | values | join "," }}
+  superUserRoles: {{ .Values.auth.superUsers | values | sortAlpha | join "," }}
   {{- end }}
   {{- if eq .Values.auth.authentication.provider "jwt" }}
   # token authentication configuration