fix: race in delete user functionality (#13547)

- The race happens with a goroutine that refreshes IAM cache data from storage.
- It could lead to deleted users re-appearing as valid live credentials.
- This change also causes CI to run tests without a race flag (in addition to
running it with).

cmd/test-utils_test.go

@@ -350,7 +350,7 @@ func UnstartedTestServer(t TestErrHandler, instanceType string) TestServer {
 
 	initAllSubsystems(ctx, objLayer)
 
-	globalIAMSys.Init(ctx, objLayer, globalEtcdClient)
+	globalIAMSys.Init(ctx, objLayer, globalEtcdClient, 2*time.Second)
 
 	return testServer
 }