MB-51558: Fix ScheduleCancelx2 intermittent failure

We occasionally see this test fail for the CB3 pool because
registerTaskable() also starts up n workers which are actually
running during this test. This test assumes 0 running workers to
poke the state properly so we should move the setting of NonIO
threads to 0 to after the registerTaskable call.

Change-Id: Ie3b5f1ed93182c67eb288789c23e14c7962ba133
Reviewed-on: https://review.couchbase.org/c/kv_engine/+/172612
Reviewed-by: Dave Rigby <[email protected]>
Tested-by: Build Bot <[email protected]>

Author: BenHuddleston

engines/ep/tests/module_tests/executorpool_test.cc

@@ -706,10 +706,13 @@ TYPED_TEST(ExecutorPoolTest, ScheduleCancelx2) {
     // (Note: makePool assumes '0' means "auto-configure" for thread counts,
     // hence must make explicit call to setNonIO(0) after construction.)
     this->makePool(1, 1, 1, 1);
-    this->pool->setNumNonIO(0);
     NiceMock<MockTaskable> taskable;
     this->pool->registerTaskable(taskable);
 
+    // registerTaskable also starts workers for the CB3 pool so we must set our
+    // workers back to 0 after.
+    this->pool->setNumNonIO(0);
+
     // Setup - simple test task which does nothing.
     // 1 hour - i.e. we don't want it to run when initially scheduled.
     auto sleepTime = 60.0 * 60.0;