[2158] added a new message id for logging

It would be logged when b10-xfrout receives the "getstats" command from the
b10-stats daemon.

src/bin/xfrout/xfrout_messages.mes

@@ -107,6 +107,10 @@ received from the configuration manager.
 The xfrout daemon received a command on the command channel that
 NOTIFY packets should be sent for the given zone.
 
+% XFROUT_RECEIVED_GETSTATS_COMMAND received command to get statistics data
+The xfrout daemon received a command on the command channel that
+statistics data should be sent to the stats daemon.
+
 % XFROUT_PARSE_QUERY_ERROR error parsing query: %1
 There was a parse error while reading an incoming query. The parse
 error is shown in the log message. A remote client sent a packet we