The case when AsyncAppend exists also in the qual of Async ForeignScan

Hi,

I found one bug. Look at the case:

CREATE TABLE test (x int) PARTITION BY HASH (x);
CREATE TABLE test_1 (x int);
CREATE TABLE test_2 (x int);
CREATE FOREIGN TABLE ftest_1 PARTITION OF test
    FOR VALUES WITH (modulus 2, remainder 0)
    SERVER loopback OPTIONS (table_name 'test_1');
CREATE FOREIGN TABLE ftest_2 PARTITION OF test
    FOR VALUES WITH (modulus 2, remainder 1)
    SERVER loopback2 OPTIONS (table_name 'test_2');
INSERT INTO test (SELECT * FROM generate_series(1,10));
ANALYZE test,test_1,test_2,ftest_1,ftest_2;

EXPLAIN (ANALYZE)
SELECT * FROM test WHERE x NOT IN (
    SELECT avg(x) FROM test WHERE x > 10
);
ERROR:  InstrEndLoop called on running node

When I added ', COSTS OFF, SUMMARY OFF, TIMING OFF' this example fall 
down into the SEGFAULT.

I prepared quick fix for this problem (see patch in attachment). Maybe 
it is'nt a best solution but it can speedup search of it.

-- 
regards,
Andrey Lepikhov
Postgres Professional