Bug 28392: make streettype and B_streettype work with BorrowerUnwantedField

Bug 28392: make streettype and B_streettype work with BorrowerUnwantedField

To test:
1. Add values to the AV ROADTYPE
2. Go to the BorrowerUnwantedField system preference and attempt to hide streettype and B_streettype.
3. It doesn't work, the fields still show.
4. Apply patch
5. Repeat step 2, it should work now.

Signed-off-by: Andrew Fuerste-Henry <andrew@bywatersolutions.com>
Signed-off-by: Joonas Kylmälä <joonas.kylmala@iki.fi>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>
Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>