Bug 24511: Update variable names to avoid confusion

Bug 24511: Update variable names to avoid confusion

To test:
1 - Create a report
    SELECT borrowernumber, firstname, surname, email, emailpro FROM borrowers WHERE surname='acosta'
2 - Create or edit patron with surname acosta to have a separate email and emailpro
3 - perl misc/cronjobs/patron_emailer --notice HOLDS --module reserves --verbose --email emailpro --report ## --from 'me@you.us'
4 - Note email is used, not email pro
5 - Apply patch
6 - Repeat, correct eamil is used

Signed-off-by: Kelly McElligott <kelly@bywatersolutions.com>
Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>