postgres_fdw: Fix failing regression test.

Commit ab3f008a2d broke this.

Report by Stephen Frost.

Discussion: http://postgr.es/m/20171205180342.GO4628@tamriel.snowman.net

contrib/postgres_fdw/expected/postgres_fdw.out

@@ -2315,7 +2315,7 @@ SELECT ft5, ft5.c1, ft5.c2, ft5.c3, ft4.c1, ft4.c2 FROM ft5 left join ft4 on ft5
 (4 rows)
 
 -- check join pushdown in situations where multiple userids are involved
-CREATE ROLE regress_view_owner;
+CREATE ROLE regress_view_owner SUPERUSER;
 CREATE USER MAPPING FOR regress_view_owner SERVER loopback;
 GRANT SELECT ON ft4 TO regress_view_owner;
 GRANT SELECT ON ft5 TO regress_view_owner;

contrib/postgres_fdw/sql/postgres_fdw.sql

@@ -560,7 +560,7 @@ SELECT ft5, ft5.c1, ft5.c2, ft5.c3, ft4.c1, ft4.c2 FROM ft5 left join ft4 on ft5
 SELECT ft5, ft5.c1, ft5.c2, ft5.c3, ft4.c1, ft4.c2 FROM ft5 left join ft4 on ft5.c1 = ft4.c1 WHERE ft4.c1 BETWEEN 10 and 30 ORDER BY ft5.c1, ft4.c1;
 
 -- check join pushdown in situations where multiple userids are involved
-CREATE ROLE regress_view_owner;
+CREATE ROLE regress_view_owner SUPERUSER;
 CREATE USER MAPPING FOR regress_view_owner SERVER loopback;
 GRANT SELECT ON ft4 TO regress_view_owner;
 GRANT SELECT ON ft5 TO regress_view_owner;