Bug 14200: GetNormalizedISBN failing to normalize valid ISBNs in some cases

Bug 14200: GetNormalizedISBN failing to normalize valid ISBNs in some cases

For some reason the regular expression used to split the multiple ISBN
fields can fail which keeps Business::ISBN from being able to parse out
and return a valid isbn. Using split() instead of the regex fixes the
issue.

Test Plan:
1) Apply the unit test patch first
2) prove t/Koha.t
3) Note the failures
4) Apply the second patch
5) prove t/Koha.t
6) Note all tests pass

Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>
Signed-off-by: Karen Bryant <kbryant@ccpl-fl.net>
Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl>
Signed-off-by: Tomas Cohen Arazi <tomascohen@gmail.com>