Start using dnsmasq as the initial dns server

So far we have not been using dnsmasq for DNS queries, we just used it
to configure public dns server addresses in the VM. Therefore, all the
dns queries hit to a public dns server after the VM, for sure. Now, we
configure dnsmasq to also run as a dns server. This way, if the address
is cached locally in the dnsmasq, we skip going to a public server and
respond locally from the host. To be able to do that, we assign a
private ipv6 address to the dnsmasq server, make it listen there and as
part of the DHCP requests, we send the dnsmasq's address to the client
as the dns server.

rhizome/host/lib/vm_setup.rb

@@ -347,17 +347,26 @@ def cloudinit(unix_user, public_key, nics)
     end.join("\n")
 
     raparams = nics.map { "ra-param=#{_1.tap}" }.join("\n")
-
+    interfaces = nics.map { "interface=#{_1.tap}" }.join("\n")
+    dnsmasq_address_ip6 = NetAddr::IPv6Net.parse(nics.first.net6).nth(3)
     vp.write_dnsmasq_conf(<<DNSMASQ_CONF)
 pid-file=
 leasefile-ro
 enable-ra
 dhcp-authoritative
+domain-needed
+bogus-priv
+no-resolv
 #{raparams}
+#{interfaces}
 dhcp-range=#{guest_network.nth(2)},#{guest_network.nth(2)},#{guest_network.netmask.prefix_len}
 #{private_ip_dhcp}
-dhcp-option=option6:dns-server,2620:fe::fe,2620:fe::9
-dhcp-option=option:dns-server,149.112.112.112,9.9.9.9
+server=149.112.112.112
+server=9.9.9.9
+server=2620:fe::fe
+server=2620:fe::9
+dhcp-option=option6:dns-server,#{dnsmasq_address_ip6}
+listen-address=#{dnsmasq_address_ip6}
 dhcp-option=26,1400
 DNSMASQ_CONF