common/munin: workaround some bug where 'host *' would bind only on ipv6

Some nonesense like:
|2018/03/15-23:08:59 Munin::Node::Server (type Net::Server::Fork) starting! pid(10504)
|Resolved [*]:4949 to [::]:4949, IPv6
|Not including resolved host [0.0.0.0] IPv4 because it will be handled by [::] IPv6
|Binding to TCP port 4949 on host :: with IPv6
Signed-off-by: Mattia Rizzolo <mapreri@ubuntu.com>

roles/common/templates/munin/munin-node.conf

@@ -57,7 +57,7 @@ allow ^178\.62\.47\.107$  # savidlin.m.o, aka munin.mapreri.org
 # cidr_deny  192.0.2.42/32
 
 # Which address to bind to;
-host *
+host 0.0.0.0
 # host 127.0.0.1
 
 # And which port