search: fix elasticsearch testsuite
search: fix elasticsearch testsuite

* Fixes test for elasticsearch query generator.

Signed-off-by: Marco Neumann <3829486b93ec44395f0b980424bae9b6fb07b7bc@crepererum.net>

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