Bug 4319: (QA follow-up) Consistency in IsAvailableForItemLevelRequest

Bug 4319: (QA follow-up) Consistency in IsAvailableForItemLevelRequest

[1] For consistency going back to IsItemOnHoldAndFound in this sub.
    This call is used in the on_shelf_holds == 2 case too.
    The routine will be refactored quite soon.
    Adding the else branch for on_shelf_holds == 0 for more clarity.
[2] Removing the test for found==F in reserves. In Koha F is only used
    when the hold is filled and moved to oldreserves.

Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>