Add note about the sudo password.

Author: kevinbackhouse

rsyslog/CVE-2018-1000140_snprintf_librelp/README.md

@@ -31,6 +31,8 @@ In the docker container for the benevolent client (terminal 1):
 sudo rsyslogd -f benevolent/rsyslog-server.conf
 ```
 
+Note: the docker image is configured so that the `sudo` password is "x".
+
 In the docker container for the server (terminal 2), start the benevolent client:
 
 ```