libsemanage: Include user name in ROLE_REMOVE audit events

Use "previous" user name when no new user is available in
semanage_seuser_audit. Otherwise "id=0" is logged instead of
"acct=user_name" ("id=0" is hard coded value).

Fixes: https://bugzilla.redhat.com/show_bug.cgi?id=1622045
1 file changed