TestToUTF8WithFallback is the cause of recurrent spurious test failures
even despite code to set the detected charset order.
The reason why this happens is because the preferred detected charset order
is not being initialised for these tests.
This PR simply ensures that this is set at the start of each test and would
allow different tests to be written to allow differing orders.
Replaces #12571Close#12571
Signed-off-by: Andrew Thornton <art27@cantab.net>
e429c1164e