Changed qdatastream unittest to remove the test file it creates.

- Remove datastream.tmp file after test completed.

Change-Id: I844600f0a477397d129fd01ac755183c2d874da4
Reviewed-by: Kurt Korbatits  <kurt.korbatits@nokia.com>
Reviewed-by: Jason McDonald <jason.mcdonald@nokia.com>
Reviewed-by: Rohan McGovern <rohan.mcgovern@nokia.com>

tests/auto/corelib/io/qdatastream/tst_qdatastream.cpp

@@ -285,6 +285,7 @@ void tst_QDataStream::getSetCheck()
 void tst_QDataStream::cleanupTestCase()
 {
     QFile::remove(QLatin1String("qdatastream.out"));
+    QFile::remove(QLatin1String("datastream.tmp"));
 }
 
 static int dataIndex(const QString &tag)