Back-patch "Fix parallel hash join path search."

Back-patch commit 655393a to 9.6.  This
synchronizes the relavant code and helps in generating parallel paths in
some cases in 9.6.  This also helps in back-patch of future patches where
we can get the same plan in all branches.

Discussion: https://postgr.es/m/CAA4eK1+XK_875cJA1HPVpx9C7C8Fp7i4QzLJ17T3igfU2iadxQ@mail.gmail.com

Author: Amit Kapila

src/backend/optimizer/path/joinpath.c

@@ -1469,17 +1469,17 @@ hash_inner_and_outer(PlannerInfo *root,
 			/*
 			 * Normally, given that the joinrel is parallel-safe, the cheapest
 			 * total inner path will also be parallel-safe, but if not, we'll
-			 * have to search cheapest_parameterized_paths for the cheapest
-			 * safe, unparameterized inner path.  If doing JOIN_UNIQUE_INNER,
-			 * we can't use any alternative inner path.
+			 * have to search for the cheapest safe, unparameterized inner
+			 * path.  If doing JOIN_UNIQUE_INNER, we can't use any alternative
+			 * inner path.
 			 */
 			if (cheapest_total_inner->parallel_safe)
 				cheapest_safe_inner = cheapest_total_inner;
 			else if (save_jointype != JOIN_UNIQUE_INNER)
 			{
 				ListCell   *lc;
 
-				foreach(lc, innerrel->cheapest_parameterized_paths)
+				foreach(lc, innerrel->pathlist)
 				{
 					Path	   *innerpath = (Path *) lfirst(lc);