Bug 17069: Koha::Patron::Category->store must default checkprevcheckout to 'inherit'

Bug 17069: Koha::Patron::Category->store must default checkprevcheckout to 'inherit'

Creating a new patron category raises an error "An error occurred when updating
this patron category. Perhaps it already exists."
DBIx::Class does not default to the value defined at the DB devel if the
key checkprevcheckout has been passed to the constructor.
We may need to provide a global fix for this kind of issue: if a column
is defined as "not null" but has a default value, the constructor
(Koha::Object->new) should not pass it to the DBIx::Class constructor
(even if assuming that null means default is a terrible mysqlism).

Test plan:
Create a new patron category.

Works as expected.
Signed-off-by: Marc <veron@veron.ch>
Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>