Bug 18094: Only search in searchable patron attributes if searching in standard fields

Bug 18094: Only search in searchable patron attributes if searching in standard fields

Test plan:
- Add a new patron attrbute and mark it searchable
- Populate a new patron with 'potato' in that field
- Add/edit another patron to have email potato@invalidemail.com'
- Perform a patron search with query 'potato' (in standard fields)
=> Both patrons are returned
- Perform a patron search with filters 'Email' and query 'potato'
=> Only 1 patron is returned and you are redirected to the patron detail page.

Followed test plan, works as expected.
Signed-off-by: Marc Véron <veron@veron.ch>
Signed-off-by: Nick Clemens <nick@bywatersolutions.com>
Signed-off-by: Brendan A Gallagher <brendan@bywatersolutions.com>