Add possibility to manage default_ttl for designate.conf

Related-Prod: PROD-35677
Change-Id: I5e423b1ecffa71e0002465b761fb91f0f9f42732
diff --git a/designate/files/queens/designate.conf.Debian b/designate/files/queens/designate.conf.Debian
index 671ae05..56e2a80 100644
--- a/designate/files/queens/designate.conf.Debian
+++ b/designate/files/queens/designate.conf.Debian
@@ -29,6 +29,9 @@
 
 # TTL Value (integer value)
 #default_ttl = 3600
+{%- if server.default_ttl is defined %}
+default_ttl = {{ server.default_ttl }}
+{%- endif %}
 
 # SOA refresh-min value (integer value)
 # Deprecated group/name - [DEFAULT]/default_soa_refresh