Ticket 48924 - Fixup tombstone task needs to set proper flag when updating tombstones
    
    Bug Description:  The fixup tombstone task is not updating tombstones due to
                      TOMBSTONE_INCLUDE not being set when looking up the entry to
                      modify.
    
    Fix Description:  If fixing up tombstones called find_entry2modify_only_ext with
                      the TOMBSTONE_INCLUDED flag.
    
    https://fedorahosted.org/389/ticket/48924
    
    Reviewed by: nhosoi(Thanks!)
    
    (cherry picked from commit 8cfb650170bbb4f6ce328b827dc294437ee38c4b)