The main purpose of audit logging is to understand who did what to the
system configuration, so it is useful to log also the list of changed
properties when a connection is updated:

 op="connection-update"
 uuid="2f3e48fc-5f47-41d9-9278-d2871378df43"
 name="pppoe1"
 args="pppoe.username,pppoe.password"         <========
 pid=9523
 uid=1001
 result="success"