roles/named: Support logging queries to syslog

This commit adds two new variables to the *named* role:
`named_queries_syslog` and `named_rpz_syslog`.  These variables control
whether BIND will send query and RPZ log messages to the local syslog
daemon, respectively.

group_vars/pyrocufflink-dns.yml

@@ -9,6 +9,8 @@ named_allow_query:
 named_dnssec_validation: false
 named_response_policy:
 - zone "blackhole.rpz"
+named_queries_syslog: true
+named_rpz_syslog: true
 
 pyrocufflink_common_zones:
 - zone: pyrocufflink.blue