Fix small query-lifespan memory leak in bulk updates.
When there is an identifiable REPLICA IDENTITY index on the target table,
heap_update leaks the id_attrs bitmapset. That's not many bytes, but it
adds up over enough rows, since the code typically runs in a query-lifespan
context. Bug introduced in commit
e55704d8b, which did a rather poor job
of cloning the existing use-pattern for RelationGetIndexAttrBitmap().
Per bug #14293 from Zhou Digoal. Back-patch to 9.4 where the bug was
introduced.
Report: <
20160824114320.15676.45171@wrigleys.postgresql.org>