Fix ordering bug in extensions/cl_khr_command_buffer/command_buffer_t…

…est_barrier.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, PoCL would occassionally start executing
the out-of-order queue while the zeroing commands were still running.

test_conformance/extensions/cl_khr_command_buffer/command_buffer_test_barrier.cpp

@@ -96,6 +96,9 @@ 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, &Ev);
         event.reset(Ev);