Bug 31565: Fix datatables searching escape for exact search

Bug 31565: Fix datatables searching escape for exact search

To test:
1. Add a new patron category with categorycode 'TEST_CAT'
2. Add a patron to category 'TEST_CAT'
3. Go to Patrons search view
4. Under "Search for patron" filters, filter by category you created at step 1
5. Click Search
6. Observe no results
7. Apply this patch and reload
8. Repeat 3-5
9. Observe expected result

Double check tests from Bug 30393 still work as expected:

10. Go to the cities page
11. Add two cities:
   - 'Cordoba %'
   - 'Buenos Aires _'
   - 'London \'
12. Use the column search on the name, alternating _, \ and % as the query
=> SUCCESS: Filtering works correctly!

Signed-off-by: David Nind <david@davidnind.com>
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>