tst_qsqlthread: Add debug about when threads finished.

Useful if someone is ever forced to try diagnose what goes wrong with this test.

Change-Id: I4b5e607e6329b6ebad2b40b3f65d6cacbb6b7fcf
Reviewed-by: Gunnar Sletta <gunnar@sletta.org>

tests/auto/sql/kernel/qsqlthread/tst_qsqlthread.cpp

@@ -77,7 +77,10 @@ public slots:
     void cleanup();
 
 protected slots:
-    void threadFinished() { ++threadFinishedCount; }
+    void threadFinished() {
+        ++threadFinishedCount;
+        qDebug("Thread finished, total finished: %d", threadFinishedCount);
+    }
 
 private slots:
     void simpleThreading_data() { generic_data(); }