Bug 29847: Make Koha::Patron::HouseboundProfile->housebound_visits return a resultset

Bug 29847: Make Koha::Patron::HouseboundProfile->housebound_visits return a resultset

This patch makes the method consistent with the rest of the codebase, by
making it return a proper resultset.

To test:
1. Run:
   $ kshell
  k$ prove t/db_dependent/Patron/HouseboundProfiles.t
=> SUCCESS: Tests pass!
2. Apply this patch
3. Repeat 1
=> SUCCESS: Tests pass!
4. Check the UI hasn't got broken either.
=> SUCCESS: It hasn't!
5. Sign off :-D

Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>
Signed-off-by: Fridolin Somers <fridolin.somers@biblibre.com>