IMPALA-13971: Deflake TestAdmissionController.test_user_loads_rules

TestAdmissionController.test_user_loads_rules is flaky for not failing
the last query that should exceed the user quota. The test executes
queries in a round-robin fashion across all impalad. These impalads are
expected to synchronize user quota count through statestore updates.

This patch attempts to deflake the test by raising the heartbeat wait
time from 1 heartbeat period to 3 hearbeat periods. It also changes the
reject query to a fast version of SLOW_QUERY (without sleep) so the test
can fail fast if it is not rejected.

Testing:
Loop the test 50 times and pass them all.

Change-Id: Ib2ae8e1c2edf174edbf0e351d3c2ed06a0539f08
Reviewed-on: http://gerrit.cloudera.org:8080/22787
Reviewed-by: Riza Suminto <riza.suminto@cloudera.com>
Tested-by: Riza Suminto <riza.suminto@cloudera.com>

tests/custom_cluster/test_admission_controller.py

@@ -1406,14 +1406,14 @@ class TestAdmissionController(TestAdmissionControllerBase):
       query_handles.append(query_handle)
 
     # Let state sync across impalads.
-    wait_statestore_heartbeat()
+    wait_statestore_heartbeat(num_heartbeat=3)
 
     # Another query should be rejected
     impalad = self.cluster.impalads[limit % 2]
     client = impalad.service.create_hs2_client(user=user)
     client.set_configuration({'request_pool': pool})
     try:
-      client.execute(SLOW_QUERY)
+      client.execute('select count(*) from functional.alltypes')
       assert False, "query should fail"
     except IMPALA_CONNECTION_EXCEPTION as e:
       # Construct the expected error message.