Add powerdns backend support

Change-Id: I44119ba5b3641646471f054acd7791a0a0d473e2
PROD: https://mirantis.jira.com/browse/PROD-11411
diff --git a/designate/files/mitaka/pools.yaml b/designate/files/mitaka/pools.yaml
index 8cc8a63..33218fe 100644
--- a/designate/files/mitaka/pools.yaml
+++ b/designate/files/mitaka/pools.yaml
@@ -55,6 +55,8 @@
         rndc_host: {{ target.options.rndc_host }}
         rndc_port: {{ target.options.rndc_port }}
         rndc_key_file: {{ target.options.rndc_key_file }}
+        {%- elif target.type == 'powerdns' %}
+        connection: {{ target.options.connection }}
         {%- endif %}
     {% endfor -%}
 
diff --git a/designate/files/ocata/pools.yaml b/designate/files/ocata/pools.yaml
index 8cc8a63..33218fe 100644
--- a/designate/files/ocata/pools.yaml
+++ b/designate/files/ocata/pools.yaml
@@ -55,6 +55,8 @@
         rndc_host: {{ target.options.rndc_host }}
         rndc_port: {{ target.options.rndc_port }}
         rndc_key_file: {{ target.options.rndc_key_file }}
+        {%- elif target.type == 'powerdns' %}
+        connection: {{ target.options.connection }}
         {%- endif %}
     {% endfor -%}