Bug 24333: Add password class to AutoSelfCheck syspref

Bug 24333: Add password class to AutoSelfCheck syspref

To test:
1 - Go to Administration
2 - Search sysprefs for AutoSelfCheck
3 - Enter something into AutoSelfCheckPass
4 - Note it is not masked
5 - Apply patch
6 - Reload page
7 - Note password is now masked

Signed-off-by: Lucas Gass <lucas@bywatersolutions.com>
Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl>
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>
Signed-off-by: Joy Nelson <joy@bywatersolutions.com>