Bug 32232: Ignore DST when calculating patron age

Bug 32232: Ignore DST when calculating patron age

This change calculates patron age using the floating timezone, so that
datetimes missing midnight don't cause fatal errors in the comparison.

Test plan:
0. Apply patch
1. Change <timezone></timezone> in koha-conf.xml to include Canada/Eastern
2. koha-plack --restart kohadev
3. Create a patron, setting the date of birth to one of these three dates
- 1947-04-27
- 1948-04-25
- 1949-04-24
4. Save the patron
5. Patron detail page loads instead of producing fatal error

Signed-off-by: Marius Mandrescu <marius.mandrescu@inLibro.com>
Signed-off-by: Nick Clemens <nick@bywatersolutions.com>
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>