Fix UB bug in extensions/cl_khr_command_buffer/command_buffer_test_ba…

…rrier.cpp

BarrierWithWaitListKHR::Run in command_buffer_test_barrier.cpp contains a
"check second enqueue" which tries to zero out the cl_mems before enqueueing
the command buffer again. However, the zeroing commands are enqueued to the
in-order queue, while the command buffer to the out-of-order queue. Since there
is no implicit or explicit sync, this is undefined behaviour.

test_conformance/extensions/cl_khr_command_buffer/command_buffer_test_barrier.cpp

@@ -93,6 +93,9 @@ struct BarrierWithWaitListKHR : public BasicCommandBufferTest
                                 0, data_size(), 0, nullptr, nullptr);
         test_error(error, "clEnqueueFillBufferKHR failed");
 
+        error = clFinish(queue);
+        test_error(error, "clFinish");
+
         error = clEnqueueCommandBufferKHR(
             0, nullptr, out_of_order_command_buffer, 0, nullptr, &event);
         test_error(error, "clEnqueueCommandBufferKHR failed");