fix(suse): preserve pool.conf

The file is managed by RPM - if purging is enabled, idempotency would
break after package updates place the Salt removed file back. Hence
exclude this file by managing it if it exists. In the default formula
configuration it is not included anyways.

Signed-off-by: Georg Pfuetzenreuter <mail@georg-pfuetzenreuter.net>

chrony/config/file.sls

     - clean: True
     - require:
       - sls: {{ sls_package_install }}
+      - file: chrony-config-file-file-managed
+      - file: chrony-config-file-pool-file-managed
 {%- endif %}
 
 chrony-config-file-file-managed:
         chrony: {{ chrony|json }}
     - require:
       - sls: {{ sls_package_install }}
+
+chrony-config-file-pool-file-managed:
+  file.managed:
+    - name: {{ chrony.confd }}/pool.conf
+    - create: False
+    - replace: False
+    - require:
+      - sls: {{ sls_package_install }}