models: logo url fix
models: logo url fix

* Fixes issue with logo url using url_for with API endpoint not
  available in UI app.

Signed-off-by: Lars Holm Nielsen <7eaffca9f7cd98839b5821d0d23e09ff764b82cd@cern.ch>

inveniosoftware/invenio-communities,inveniosoftware/invenio-communities,inveniosoftware/invenio-communities,inveniosoftware/invenio-communities