pam: Use cache for users with existing session
    
    Users that have an existing session do the bulk of their authentication
    to unlock services that do not make use of initgroups (used only to
    create a new login session). Forcing online initgroups calls for these
    users leads mostly to delays in providing those services and do not
    provide any useful data.
    
    Resolves:
    https://pagure.io/SSSD/sssd/issue/4098
    Signed-off-by: Simo Sorce <simo@redhat.com>
    
    Reviewed-by: Pavel Březina <pbrezina@redhat.com>