Bug 27593: Consistent behavior for club holds route

Bug 27593: Consistent behavior for club holds route

This patch:
- Fixes a malformed response when biblio_id is invalid
- Fixes the return status (400 => 404) when biblio_id is invalid
- Adapts the error strings to be consistent with the Cities.pm file

To test:
1. Apply the regression tests patch
2. Run:
   $ kshell
  k$ prove t/db_dependent/api/v1/clubs_holds.t
=> FAIL: Tests fail
3. Apply this patch
4. Repeat 2
=> SUCCESS: Tests pass!
5. Sign off :-D

Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>
Signed-off-by: David Nind <david@davidnind.com>
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>