opt: deflake fk_read_committed

Previously the async portion of the fk_cascade_race subtest had ... a
race. Usually the test would follow the intended route where the async
statements are executed in the same session as the previous statements,
but this was not guaranteed by logictest. By moving the racing statement
to the testuser, we force this serialization so that we don't get
periodic test failures.

Fixes: #150466
Release note: None

Author: mw5h

pkg/ccl/logictestccl/testdata/logic_test/fk_read_committed

@@ -117,9 +117,17 @@ CREATE TABLE child_150282 (
   INDEX (p)
 );
 
+statement ok
+GRANT ALL ON TABLE parent_150282 TO testuser;
+
+statement ok
+GRANT ALL ON TABLE child_150282 TO testuser;
+
 statement ok
 INSERT INTO parent_150282 VALUES (1, 2, 3);
 
+user root
+
 statement ok
 BEGIN ISOLATION LEVEL READ COMMITTED;
 
@@ -129,14 +137,20 @@ SELECT 1;
 statement async fk_delete
 WITH sleep AS (SELECT pg_sleep(1)) DELETE FROM parent_150282@parent_150282_i_idx WHERE i = 2;
 
+user testuser
+
 statement ok
 INSERT INTO child_150282 VALUES (4, 1);
 
+user root
+
 awaitstatement fk_delete
 
 statement ok
 COMMIT;
 
+user testuser
+
 query III
 SELECT * FROM parent_150282;
 ----
@@ -148,6 +162,8 @@ SELECT * FROM child_150282;
 statement ok
 INSERT INTO parent_150282 VALUES (1, 2, 3);
 
+user root
+
 statement ok
 BEGIN ISOLATION LEVEL READ COMMITTED;
 
@@ -157,9 +173,13 @@ SELECT 1;
 statement async fk_update
 WITH sleep AS (SELECT pg_sleep(1)) UPDATE parent_150282 SET p = 4 WHERE i = 2;
 
+user testuser
+
 statement ok
 INSERT INTO child_150282 VALUES (4, 1);
 
+user root
+
 awaitstatement fk_update
 
 statement ok