Bug 5343: It is not possible to add a subscription for another supplier

Bug 5343: It is not possible to add a subscription for another supplier

If a supplier is defined for a subscription, you cannot order this
subscription to another supplier. If no supplier is defined, you can.

FIX: If a cancelled order is linked to a subscription, you can order it.

Signed-off-by: Leila Arkab <koha.aixmarseille@gmail.com>
Signed-off-by: Katrin Fischer <Katrin.Fischer.83@web.de>
Signed-off-by: Jared Camins-Esakov <jcamins@cpbibliography.com>