dnsmasq: store leases in sqlite database

To avoid dnsmasq writing out the whole leasefile on each request
before replying. This gets slow on high‐latency storage.

Also tweak DNS updates a bit.

roles/dnsmasq/templates/00-options.conf.j2

@@ -18,4 +18,8 @@ interface = {{ interfaces | map(attribute='name') | join(',') }}
 dhcp-option = option:dns-server,{{ dns | join(',') }}
 dhcp-option = option:ntp-server,{{ ntp | join(',') }}
 
-dhcp-script = /usr/local/bin/dns-update
+dhcp-script = /usr/local/bin/dnsmasq-script
+dhcp-scriptuser = dnsmasq
+
+# track leases with dnsmasq-script instead
+leasefile-ro