Bug 14576: Replaced calls using deprecated method GetItem with Koha::Items->find

Bug 14576: Replaced calls using deprecated method GetItem with Koha::Items->find

Test plan:
1) Apply all patches except this one
2) Checkout out an item to a patron
3) Check the item in - note that this will fail
4) Apply this patch, and repeat steps 1-3, noting instead that the the
check is instead successful
5) Verify also that reserves act as expected
5) Sign off

Sponsored-by: Catalyst IT

Signed-off-by: Liz Rea <wizzyrea@gmail.com>

Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>

Signed-off-by: Nick Clemens <nick@bywatersolutions.com>