WebSearch: unit test update

* Amends the tests test_parsing_structured_query_existing_field
  and test_parsing_colons_and_spaces_badly_structured to use
  more common fields to keep the tests from failing on some
  production sites due to different non-Atlantis index
  configurations these sites may have.  (closes #1326)

* Fixes typos in test functions.

Co-authored-by: Alessio Deiana <alessio.deiana@cern.ch>
Reviewed-by: Tibor Simko <tibor.simko@cern.ch>