Bug 8509: allows the Expected status to be chosen back

Bug 8509: allows the Expected status to be chosen back

If a serial has been marked as received by mistake, it's now
possible to set it as an "Expected" serial again.

Signed-off-by: Melia Meggs <melia@test.bywatersolutions.com>
Signed-off-by: Katrin Fischer <Katrin.Fischer.83@web.de>
Passes all tests and QA script.

I did varoius tests on a subscription switching between the
different status (expected, arrived, late) and couldn't find
a bad side effect of this patch.

Note: The date arrived/date expected is not automatically reset,
but you can enter the date manually in the template, so I think
this could be handled in a separate bug.
Signed-off-by: Jared Camins-Esakov <jcamins@cpbibliography.com>