LP#1322303 cleanse backdate for checkin overdue voiding

Passing raw backdates, particularly from offline transactions, which
have a space between the date and time, to
DateTime::Format::ISO8601->parse_datetime results in "Invalid date
format:" errors.  Pass the date through the cleanse routine first.

Signed-off-by: Bill Erickson <berick@esilibrary.com>
Signed-off-by: Ben Shum <bshum@biblio.org>