Refactor the IPv6 bridge torrc template to use orport-v6.i

torrc_templates/bridge-v6.tmpl

@@ -1,3 +1,4 @@
 ${include:bridge.tmpl}
 
-OrPort ${ipv6_addr}:${orport} IPv6Only
+# A bridge that has an IPv6 ORPort
+${include:orport-v6.i}