examples: fix example application
examples: fix example application

* Removes the user activation step in documentation since the user is
  activated during the creation process.

* Fixes the check of registered usery.

Signed-off-by: Javier Delgado <5e5ca04284d36f70c75026b19c877319dd719efc@cern.ch>

tiborsimko/invenio-search,inveniosoftware/invenio-search,tiborsimko/invenio-search,inveniosoftware/invenio-search