Using citus.force_max_query_parallelization=1 for failure_distributed_results causes it to fail

Normally it should fetch intermediate results from the other node when the connection to the first is broken, but if `citus.max_adaptive_executor_pool_size` is set to `1` a hard failure occurs.

```diff
SELECT resultId, nodeport, rowcount, targetShardId, targetShardIndex
FROM partition_task_list_results('test', $$ SELECT * FROM source_table $$, 'target_table')
NATURAL JOIN pg_dist_node;
-WARNING: connection to the remote node localhost:xxxxx failed with the following error: connection not open
+ERROR: connection to the remote node localhost:9060 failed with the following error: connection not open
SELECT * FROM distributed_result_info ORDER BY resultId;
- resultid | nodeport | rowcount | targetshardid | targetshardindex
----------------------------------------------------------------------
- test_from_100800_to_0 | 9060 | 22 | 100805 | 0
- test_from_100801_to_0 | 57637 | 2 | 100805 | 0
- test_from_100801_to_1 | 57637 | 15 | 100806 | 1
- test_from_100802_to_1 | 57637 | 10 | 100806 | 1
- test_from_100802_to_2 | 57637 | 5 | 100807 | 2
- test_from_100803_to_2 | 57637 | 18 | 100807 | 2
- test_from_100803_to_3 | 57637 | 4 | 100808 | 3
- test_from_100804_to_3 | 9060 | 24 | 100808 | 3
-(8 rows)
-
+ERROR: current transaction is aborted, commands ignored until end of transaction block
-- fetch from worker 2 should fail
SAVEPOINT s1;
+ERROR: current transaction is aborted, commands ignored until end of transaction block
SELECT fetch_intermediate_results('{test_from_100802_to_1,test_from_100802_to_2}'::text[], 'localhost', :worker_2_port) > 0 AS fetched;
-ERROR: could not open file "base/pgsql_job_cache/xx_x_xxx/test_from_100802_to_1.data": No such file or directory
-CONTEXT: while executing command on localhost:xxxxx
+ERROR: current transaction is aborted, commands ignored until end of transaction block
ROLLBACK TO SAVEPOINT s1;
+ERROR: savepoint "s1" does not exist
-- fetch from worker 1 should succeed
SELECT fetch_intermediate_results('{test_from_100802_to_1,test_from_100802_to_2}'::text[], 'localhost', :worker_1_port) > 0 AS fetched;
- fetched
----------------------------------------------------------------------
- t
-(1 row)
-
+ERROR: current transaction is aborted, commands ignored until end of transaction block
-- make sure the results read are same as the previous transaction block
SELECT count(*), sum(x) FROM
read_intermediate_results('{test_from_100802_to_1,test_from_100802_to_2}'::text[],'binary') AS res (x int);
- count | sum
----------------------------------------------------------------------
- 15 | 863
-(1 row)
-
+ERROR: current transaction is aborted, commands ignored until end of transaction block
ROLLBACk;
```

The failure originates from this part of our code, because transactionCritical has become true:
https://github.com/citusdata/citus/blob/c83c5567028d2035651c39f737ac5a944a70db16/src/backend/distributed/executor/adaptive_executor.c#L3196-L3203