[FIX] stock: reset stock move state

On a delivery, when changing the initial demand of a stock move, if its
value was 0 and becomes > 0, its state will be 'Partially Available' but
the reserved quantity will still be 0.

To reproduce the error:
1. Create 2 products P01, P02
    - Product Type: Storable
    - Qty On Hand: 1
2. Create + Confirm a SO with 1xP01 and 1xP02
3. Open SO's delivery
4. Unlock, set P01's initial demand to 0, Save, Lock
5. Unreserve, Check Availability
6. Unlock, set P01's initial demand to 1, Save
7. Click on PO1 line

Error: The stock move state is "Partially Available", but the initial
demand is 1 and the reserved quantity is 0. It should be "Waiting
Availability"

On step 5, since the wanted quantity of P01 is 0, the state of the stock
move becomes "Available". Then, when increasing the requested quantity,
the state automatically becomes "Partially Available" because the module
does not consider the case where the state is "Available" with a
reserved quantity equal to 0.

OPW-2488580

closes odoo/odoo#70661

Signed-off-by: Arnold Moyaux <amoyaux@users.noreply.github.com>