WebStyle: ping handler returning 200 status code
WebStyle: ping handler returning 200 status code

* When queried by a load-balancer (such as haproxy), this commits makes
  the /ping web handler to return HTTP status code 200, even if e.g.
  ACCESS_CONTROL_LEVEL_SITE is set to 1 (which implies returning HTTP
  error status code 503 for any other web handler so that crawlers don't
  register these requests).  (PR #2700)

Signed-off-by: Samuele Kaplun <2e218f779e12714c314fad8ebf6b3041daa21337@cern.ch>
Reviewed-by: Tibor Simko <c7116e45300b163846dc01f3ed02116e3f8ef7a5@cern.ch>

inveniosoftware/invenio,tiborsimko/invenio,tiborsimko/invenio,inveniosoftware/invenio