overrides: fixes for sysdb_invalidate_overrides()
    
    There were two issues in sysdb_invalidate_overrides().
    
    First, SYSDB_CACHE_EXPIRE was only reset for the entry in the data cache
    but not in the timestamp cache.
    
    Second, if one of the steps in the combined replace and delete operation
    failed no change was committed to the cache. If, for whatever reasons,
    a user or group object didn't had SYSDB_OVERRIDE_DN set the delete
    failed and hence SYSDB_CACHE_EXPIRE wasn't reset as well. To make sure
    the cache is in a consistent state after a view change the replace and
    the delete operations are don in two steps.
    
    Related to https://pagure.io/SSSD/sssd/issue/3579
    
    Reviewed-by: Fabiano Fidêncio <fidencio@redhat.com>