Ticket #572 - PamConfig schema not updated during upgrade
    
    Bug description: PAM passthrough schema was not upgraded in the
    upgrade from 389-ds-base-1.2.10.2 to 389-ds-base-1.2.11.15.
    
    Fix description: This patch adds 60pam-plugin.ldif to the upgrade
    schema file list.
    
    Reviewed by Nathan (Thank you!!)
    (cherry picked from commit ac6b2c94bb32fc47870a56e8f7fc109ea81a3f47)