- setup_sj_materialization() code failed to take into account that it can be that 
  the first [in join order ordering] table inside semi-join-materialization nest 
  is also an inner table wrt an outer join (that is embedded in the semi-join).  
  This can happen when all of the tables that are inside the semi-join but not inside
  the outer join are constant.
- Made a trivial to not assume that table's embedding join nest is the semi-join 
  nest: instead, walk up the outer join nests until we reach the semi-join nest.