Bug 29477: Flatpickr - default to 23:59 for the time part

Bug 29477: Flatpickr - default to 23:59 for the time part

It was defaulting to 12:00 which was an unexpected change in behaviour
caused by flatpickr switch.

Test plan:
On the circulation view, check some items out and play with the time
part and "Remember for session". The behaviour must be correct, ie. the
same as prior to flatpickr switch.

Signed-off-by: David Nind <david@davidnind.com>
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>