Bug 18244: Patron card creator does not take in account fields with underscore (B_add...

Bug 18244: Patron card creator does not take in account fields with underscore (B_address etc.)

Fields with underscore like B_address do not print on patron cards.

To reproduce:
- Create patron card layout using fields with underscore in their name
  (e.g. <surname><B_address> )
- Print (export) patron card
- Verify that fields without underscore are replaced by their value,
  but fields with underscore do not replace but show the field name

To test:
- Apply patch
- Try to reproduce and verify that fields with underscore are replace
  as expected

Signed-off-by: Christopher Brannon <cbrannon@cdalibrary.org>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>
Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>