Return Erlang node long name in metadata

Fixes #2

Author: acogoluegnes

src/rabbit_stream.erl

@@ -31,12 +31,21 @@ start(_Type, _Args) ->
 host() ->
     case application:get_env(rabbitmq_stream, advertised_host, undefined) of
         undefined ->
-            {ok, Host} = inet:gethostname(),
-            list_to_binary(Host);
+            hostname_from_node();
         Host ->
             rabbit_data_coercion:to_binary(Host)
     end.
 
+hostname_from_node() ->
+    case re:split(rabbit_data_coercion:to_binary(node()),
+                  "@",
+                  [{return, binary}, {parts, 2}]) of
+        [_, Hostname] ->
+            Hostname;
+        [_] ->
+            rabbit_data_coercion:to_binary(inet:gethostname())
+    end.
+
 port() ->
     case application:get_env(rabbitmq_stream, advertised_port, undefined) of
         undefined ->