Bug 32517: lowercase category codes to avoid mismatch

Bug 32517: lowercase category codes to avoid mismatch

To test:
1 - sudo koha-mysql kohadev
2 - UPDATE borrowers SET categorycode = LCASE(categorycode)
3 - Try to search for patrons:
    Uncaught TypeError: categories_map[data] is undefined
4 - Apply patch
5 - Search for patrons
6 - Success!

Signed-off-by: David Nind <david@davidnind.com>
Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl>
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>