Bug 23521: Put parentheses arround limit terms

Bug 23521: Put parentheses arround limit terms

Test plan:
  - Use Elasticsearch 6 (you'll need Bug 18969),
  - create a biblio (#1) with "Dillinger Girl" in author and what you
    want in title,
  - create another biblio (#2) with the word "girl" in the title and
    "Dillinger Escaplan" as author
  - reindex
  - search * and refine on "Dillinger Girl"
  - Ko => Biblio #1 and #2 appear
  - Apply this patch,
  - search * and refine on "Dillinger Girl"
  - Ok => anly biblio #1 appears
  - use Elasticsearch 5 again
  - check for no search regression

Signed-off-by: Séverine QUEUNE <severine.queune@bulac.fr>
Signed-off-by: Séverine QUEUNE <severine.queune@bulac.fr>
Signed-off-by: Nick Clemens <nick@bywatersolutions.com>
Signed-off-by: Ere Maijala <ere.maijala@helsinki.fi>
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>